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Acetylcholine and 5-hydroxytryptamine in the snail brain
Abstract
1.1. The snail contains 0.5-4 μγ 5HT/g wet weight. 5HT is also present in the heart and mantle.2.2. The brain homogenate contains and enzyme that will decarboxylate 5-hydroxytryptophan (5HTP) and the kidney can convert 5HT to 5-hydroxy indole acetic acid (5HIAA).3.3. The brain contains 1–5 μg acetylcholine/g wet weight.4.4. There are other compounds present in the snail brain that can act as cardiac accelerators.
... While limited information exists on molluscicidal modes of action, various botanical insecticides (including essential oil constituents) have been shown to act on the insect cholinergic system, GABA system, mitochondrial system, octopaminergic system, tyramine receptor system, and endocrine system (Isman and Machial 2006;Rattan 2010). Since acetylcholine and acetylcholinesterase (Kerkut and Cottrell 1963;Zaĭtseva and Kuznetsova 2008) and octopamine (Guthrie et al. 1975;Robertson and Juorio 1976) can be found in terrestrial gastropod tissues, and tyramine-positive neurons have been found in aquatic gastropods (Turner and Cottrell 1978;Osborne 1985), it is plausible that essential oils act against insects and mollusks in comparable ways. The case for this possibility is further strengthened by the activity of conventional molluscicides. ...
The gray field slug, Deroceras reticulatum, is a key pest of seed crops. There is an increasing interest in developing new chemical controls due to limited management options. Essential oils, being non-toxic to humans and exempt from pesticide registration and residue tolerance requirements under US federal law (Sect. 25(b) of the Federal Insecticide, Fungicide, and Rodenticide Act), could be safe and easily implementable alternatives. In this study, the most toxic essential oils to D. reticulatum adults of 13 plant-derived essential oils and one synthetic toxin (caffeine) were determined based on Lethal Concentration 50 values produced in a laboratory Petri dish bioassay. Thyme, spearmint, and pine oil were the most lethal, causing 50% mortality of D. reticulatum at concentrations of 0.148, 0.153, and 0.176% (v/v), respectively. Thyme and spearmint oil were then tested in a greenhouse microcosm experiment and a separate phytotoxicity assessment. In the greenhouse, slugs were added to containers planted with annual ryegrass (Lolium multiflorum) and the containers were sprayed with either 0.5% (v/v) essential oil emulsion, Slug-Fest (industry standard molluscicide), surfactant control at 1% (v/v), or water control. Both oils caused 97.5% mortality of slugs, performing comparably to metaldehyde. Phytotoxic effects were assessed by spraying oils on seedlings and adult plants of two cultivars each of perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea). No definitive signs of phytotoxicity were observed upon visual inspection, and there were no differences in chlorophyll content or biomass between treated and untreated plants.
... This began in the mid-1950s and included Tauc's ground-breaking work in Aplysia [21], which inspired Kandel's Nobel Prize winning research on learning and memory [22]. Gastropod identified neurons were not only instrumental in early advances on synapses [23,24], neurotransmitters [25], and the neural basis of behavior [26,27], they continue to enable important contributions in these areas today. ...
Gastropod molluscs have large neurons that are uniquely identifiable across individuals and across species based on neuroanatomical and neurochemical criteria, facilitating research into neural signaling and neural circuits. Novel neuropeptides have been identified through RNA sequencing and mass spectroscopic analysis of single neurons. The roles of peptides and other signaling molecules including second messengers have been placed in the context of small circuits that control simple behaviors. Despite the stereotypy, neurons vary over time in their activity in large ensembles. Furthermore, there is both intra-species and inter-species variation in synaptic properties and gene expression. Research on gastropod identified neurons highlights the features that might be expected to be stable in more complex systems when trying to identify cell types.
... Also Croll & Lo (1986) found the majority of serotonin-containing cell bodies in the pedal ganglia of Littorina littorea. A general binding of serotonin antibodies to mucus cells has also been shown by Kerkut & Cottrell (1963), Marchand & Colard (1991), and Vig et al. (1985) in the mantle, oesophagus and gut of Helix aspersa. All these results indicate that serotonin may be involved in the regulation of mucus cells in the skin of slugs. ...
Using light and electron microscopy in combination with histochemical and immunocytochemical techniques, the impact of orally
and dermally applied metaldehyde on mucus cells in the digestive tract, the skin, and the salivary gland of the slug Deroceras reticulatum (Müller) was investigated. The studies showed that metaldehyde induces severe alterations and damages in mycocytes even under
low temperature and humid conditions when sufficiently high doses were applied. After metaldehyde application, not only the
quantity of mucus produced by slugs but also its quality is modified. Structural, enzymehistochemical and immunocytochemical
investigations revealed metaldehyde-induced effects in mucocytes to be related to influences of the molluscicide on serotonin
and on energy metabolism.
The invasive golden apple snail Pomacea canaliculata is one of the devastating threats to aquatic ecosystems and wetland agriculture worldwide. Macrolides from microbes display various advantages over other compounds in controlling snails. However, emergence of antibiotic-resistant phenotypes against certain macrolides in the field appeals for exploring more effectively molluscicidal macrolides. Here, two borrelidins, borrelidin BN1 and BN2, from the extract of a Streptomyces strain fermentation were evaluated for molluscicidal potential against P. canaliculata using both immersion and contact bioassay methods. Borrelidin BN1 (borrelidin A) presented a significant molluscicidal activity comparable to the chemical pesticide metaldehyde, and had a much lower median lethal concentration value (LC50, 522.984 μg·ml-1) than avermectin B1 at 72 h of contact-killing treatment. Snail growth was inhibited by borrelidin BN1 more than by metaldehyde at sublethal concentrations, consistent with responses of key biochemical parameters. Exposure to borrelidin BN1 decreased the activity of acetylcholinesterase (AChE), glutathione S-transferase (GST), aspartate aminotransferase (AST), alanine aminotransferase (ALT) as well as the levels of energy reserves and sex steroids in snail tissues, while increased the activity of superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH) and the level of lipid peroxidation (LPO). Further application assay confirmed that borrelidin BN1 protected crop plant Zizania latifolia from P. canaliculata damage via suppressing snail population density. These findings suggest great potential of borrelidin BN1 as a molluscicide. Additionally, its higher activity than the stereoisomeric borrelidin BN2 (borrelidin F) implied better molluscicidal borrelidins could be acquired through structural optimization.
The synaptic transmitter function of 5-hydroxytryptamine (5-HT) has been discussed for many years. However, crucial evidence relating this indoleamine to the function of a specific synapse has not yet been obtained either in vertebrates or in invertebrates.
For some time past, certain pharmacological reagents which modify neuronal activity in the vertebrates, have been found to be reactive on invertebrate nervous systems (Eccles 1964; Kerkut 1967).
A study of invertebrate pharmacology can lead to observations which are of value both to vertebrate and to comparative studies. A number of invertebrate preparations are used as biological assays for compounds which are of interest to vertebrate physiologists and pharmacologists — for example, the leech (Hirudo) dorsal muscle strip as an assay procedure for acetylcholine (Fuehner 1918; Minz 1932); the quahaug [Mercenaria (Venus)] heart as an assay for 5-hydroxytryptamine [5-HT’ (serotonin)] (Welsh 1953); the crayfish stretch receptor neuron as an assay for gamma-aminobutyric acid (GABA) and for Factor I (Wiersma, Furshpan and Florey 1953; Florey 1954); and the crayfish hind gut for the assay of GABA and Factor I (Florey 1961).
Es spricht vieles dafür, daß das Auftreten des Acetylcholins, der Cholinesterasen und der Cholinacetylase mit der Ausbildung des Nervensystems in der Ontogenese zusammenfällt, resp. ihr etwas vorauseilt, wofür bei Karczmae (1963a, b) Beispiele bei Invertebraten und Vertebraten vorliegen. Nicht so einfach liegen die Verhältnisse in der Stammesentwicklung der Tiere.
Von welcher Organisationshöhe an der tierische Organismus über 5-Hydroxy-tryptamin verfügt, wissen wir nicht. Ist die Fähigkeit zur Tryptophanbildung wohl so alt wie der tierische Organismus selbst, so haben wir bei Protozoen, speziell bei Flagellaten und Ciliaten bisher keine Anhaltspunkte für den Aufbau von 5-Hydroxytryptamin. Doch ist es im weiteren Verlauf der tierischen Entwicklung bei den beiden Überträgerstoffen Acetylcholin und Noradrenalin, welche bei vielen Invertebraten und Vertebraten — und schon bei Protozoen — spezifische aktivierende oder hemmende (regulierende) Funktionen im Tierkörper ausüben, nicht geblieben. Vielleicht ist vom „Anfang“ der tierischen Organisation an 5-Hydroxytryptamin gebildet worden. Jedenfalls können wir von den Coelente-raten an im 5-Hydroxytryptamin einen hormonartigen Stoff erkennen, der durch das Tierreich bis zum Säugetier und dem Menschen zu verfolgen ist und zum Teil ähnliche Überträgerfunktionen zu besitzen scheint wie Acetylcholin oder Noradrenalin.
Quantitative data on the occurrence of 5-HT and related indolealkylamines in nature are presented in Tables 1–23 of this chapter and in Tables 1–6 of chapter 13. The interest of these data is obvious, especially for the interpretation of the physiological significance of indolealkylamines in their different localizations. However, it seems opportune to call attention at once to a few points.
All the major amine and amino acid putative transmitters occur throughout the molluscs, and many can be localized in specific neurons, particularly in gastropod central neurons. Another important marker for the presence of these compounds is the presence of specific enzymes—for example, histidine decarboxylase for histamine, tyrosine hydroxylase for dopamine, tryptophan hydroxylase for serotonin, dopamine-β-hydroxylase for noradrenaline and/or octopamine, and choline acetyltransferase for acetylcholine. All these compounds can probably function either as synaptic transmitters to produce relatively fast on-off responses or as modulators to produce slower, more sustained modulation of ongoing activity. Modulators can possibly act at many sites in the animal. These compounds can act through a number of postsynaptic mechanisms—for example, fast and slow excitatory postsynaptic potentials, fast and slow inhibitory postsynaptic potentials, and a variety of combinations of biphasic response. The molluscs provide a wide range of very useful model systems for the analysis of neurochemical, neuropharmacological, and neurophysiological processes. This chapter illustrates the dorsal and ventral views of the abdominal ganglion of Aplysia to show the positions of some identified neurons.
For a satisfactory extraction of 5-HT from tissues it is sufficient that they be carefully cleaned, minced finely with scissors and then treated with 4 parts (w/v) of pure acetone, to give a final concentration of acetone of approximately 80%.
This chapter focuses on axonal and synaptic pharmacology of the insect nervous system. It describes the mechanisms of nerve excitation and conduction and of synaptic transmission. The efficiency of drugs is a function of the ability to reach the receptor sites within the nervous tissue. The chapter further discusses the mechanism whereby ions and molecules are excluded from the nervous system. It has been shown that in insect species, the changes in the chemical composition of the medium bathing the nervous system are not reflected in equivalent changes in neuronal function. An earlier study of the rates of penetration of a number of compounds into the nervous system indicated that insect ganglia contain one or several barriers. This barrier(s) is able to discriminate against size, charge, and polarity of the molecule. It has been demonstrated that uncharged molecules penetrated easily into the central nervous system (CNS) than the charged ones. Investigations have shown that regulation could take place at different levels of the nervous system. Insects do not differ from other animal species and that the mechanisms for excitation, conduction. The synaptic transmission is not significantly different from those found in other invertebrate or vertebrate species.
This chapter reviews the neuromuscular transmission and excitation–contraction coupling in molluscan muscle. In molluscs, excitatory nerves activate brief phasic responses or prolonged tonic contractions, depending on the specific properties of the muscle fibers and the innervating neurons. The contractile mechanism is activated by calcium ions (Ca2+). The translocation of Ca2+ from outside the muscle fiber or from superficial sites on the membrane is involved directly or indirectly in excitation–contraction coupling. Individual muscle fibers may be innervated by a single excitatory neuron or by two or more excitatory neurons, each of which releases a different transmitter. The dual innervation of individual muscle fibers by inhibitory and excitatory neurons as well as by relaxing and excitatory neurons also occurs. In molluscs, neuromodulator substances (local hormones) alter metabolism via a secondary messenger. Catch is a phenomenon, highly developed in certain specialized mollusc muscles and is maintained by attached actin–myosin cross-bridges that do not cycle. During catch contraction, muscles are resistant to stretch and remain so after excitation has ceased and intracellular free Ca2+ has returned to resting levels. Catch is activated by excitatory nerves that release acetylcholine (ACh) and terminated by relaxing nerves, which release serotonin. However, increase in excitability induced by serotonin enhances the transition from the passive catch state to a state of phasic activity and that the unusual role of serotonin in relaxing catch may have evolved in connection with its more typical role as a modulator.
Cholinergic transmission in the ganglia of gastropod molluscs was recently shown by Tauc and Gerschenfeld (1962), Kerkut and Cottrell (1963), and Kerkut and Thomas (1963). However, very little is known about the properties of cholinoreceptors of mollusc neurons. For studying these cholinoreceptors, cholinergic drugs of different chemical structure have been used as a tool (Vulfius and Zeimal 1967a, 1967b). Cholinergic drugs with well-known pharmacological properties which have been widely studied in experiments on vertebrates have been chosen. In this way, we hope to compare the properties of mollusc cholinoreceptors with those of vertebrates and get some information about the occurrence and arrangement of active groups on cholinoreceptive membranes.
Anatomical studies have shown that synapses, essentially axo-axonic ones, are localized in the neuropilar region of ganglia. These synapses correspond to coupling zones of very fine nerve fibres which lie adjacent to or cross one another. In some cases these zones of contact exhibit a level of organization which is equivalent to that of synaptic knobs. The clusters of vesicles which occur along these zones seem to be mainly localized in the cytoplasm of one of a pair of fibres, usually the larger one. By analogy with the current concepts of vertebrate synaptic regions, these vesicles might be regarded as containing the ACh molecules which are released into the synaptic cleft on arrival of presynaptic impulses. The electrophysiological evidence outlined in this chapter is in essential agreement with the hypothesis of a cholinergic synaptic transmission in insects: it is presented that several anticholinesterasic substances, such as eserine and DFP (which are known to favour the accumulation of ACh. in synaptic zones and extend postsynaptic membranes depolarization) induce either intense after-discharges following a single presynaptic stimulation or in some cases a spontaneous activity. A total block of synaptic transmission then occurs, most probably as a result of an excessive depolarization of postsynaptic membranes produced by ACh.
1. Seventy per cent or more of the acetylcholine and 5-hydroxytryptamine in Mercenaria ganglia is bound to particles which sediment when homogenates of this tissue, prepared in 1·1 M glucose, are centrifuged at high speed.2.2. Similarly, a large proportion of the unidentified cardio-excitatory factor, Substance X, is particle bound in Mercenaria ganglia.3.3. Particles binding each of these substances have been partially separated from each other by density gradient centrifugation. The acetylcholine particles were mainly associated with the least dense layers of the gradient, 5-hydroxytryptamine with more dense layers and Substance X with layers of intermediate density.4.4. A fraction of 5-hydroxytryptamine particles has been purified twenty times over the original homogenate. The level of acetylcholine contamination of this fraction, if any, was below the limit of detection.5.5. Particles binding acetylcholine and 5-hydroxytryptamine release their active substances in a quantitatively similar manner to changes in pH, hypotonicity and increased temperature.
1. Paper chromatographic, gas chromatographic and spectrophotofluorimetric analysis of limpet pooled ganglion extracts showed they contained 5-HT (6·42±0·33 μg/g), dopamine (9.57±1·0 μg/g)1470 1475 V 3 and ACh (<1 μg/g). Heart extracts contained5-HT(0·97±0·1 μg/g) and ACh (<1 μg/g) but no dopamine.2. Ganglion 5-HT content was increased (to 11·76±1·58 μg/g) by pretreatment with 5-HTP, and depleted by tetrabenazine. Heart 5-HT content was increased after 5-HTP (to 1·73±0·14 μg/g), increased slightly after pretreatment with p-chlorophenylalanine if(to 1·57±0·35 μg/g) and depleted by tetrabenazine.3. Acetylcholinesterase and monoamine oxidase activities were present in ganglia and hearts.
1.1. Specific granular cells were found in the heart, mantle and subesophageal ganglia of the snails Helix aspersa and Strophocheilus oblongus.2.2. Histochemical methods for the demonstration of enterochromaffin granules gave positive results in these cells.3.3. Differential osmium reduction by nerves in these hearts showed two kinds of fibres: osmiophilic and non-osmiophilic nerves and gives histological evidence of a double innervation (inhibitory and stimulatory fibres) to the snail heart.4.4. Osmiophilic endings are reported in the ventricle and auricle and are shown to end very close to the granular cells.5.5. No neurosecretory-staining material could be traced along nerves in these hearts.6.6. One large bipolar neuron is described in these hearts.7.7. Histological preparations of the heart of Strophocheilus oblongus that had long been stimulated through its cardiac nerve show a release of the granular content in the cells and disclose stages of a secretory cycle. It is suggested that these cells are glandular tissue and perform a hormonal function.
The dart apparatus, used during courtship in some groups of hermaphroditic land snails, has long been assumed to have a “stimulatory” effect on the mating partner, though how stimulation occurs and exactly what function it serves has never been determined. In this study, extracts of the mucous glands of the dart apparatus of the land snail Helix aspersa were injected into conspecifics and into a related snail, Cepaea nemoralis , in order to test the hypothesis that the dart is used to achieve inflow of bioactive mucous gland secretions into the darted snail. Helix aspersa injected with the extract responded by everting their terminal genitals; eversion normally takes place during courtship and mating. Boiling the extract increased the bioactivity. Pronase-treated extract lost bioactivity, and gel filtration of the boiled extract indicated that the active substance has a molecular weight of about 5,000. The active substance may be a polypeptide. Cepaea nemoralis also everted their genitals when injected with the boiled Helix extract. The active substance appears to be a contact sex pheromone, the second such pheromone in a pulmonate land snail for which experimental evidence has been obtained. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/38091/1/1402380202_ftp.pdf
1.1. The anatomy and innervation of the heart in the slug Limax maximus are described.2.2. The heart is myogenic and is reflexively modulated by tactile stimulation of the body surface.3.3. Pharmacological data suggest that cardioexcitation is serotoninergic and cardioinhibition cholinergic, although both ACh and 5-HT have biphasic effects depending on concentration.4.4. Cardioexcitatory and cardioinhibitory areas of the visceral ganglion were identified and modulation of heart rate by single cells demonstrated.
1.1. Two types of morphologically differentiated neurons have been described in the viscerial ganglion of Elliptio complanatus.2.2. Axo-somatic synapses have been found on neurons of Type II N.3.3. Synapses contain clear, dense core and uniformly dense vesicles. The dense core vesicles are like catecholamine-containing vesicles described in other systems. No synapses containing only clear synaptic vesicles have been found.4.4. Fluorescence studies indicate that monoamines are present in cell bodies and in the neuropile.5.5. Vesicles morphologically identical to synaptic vesicles are also found in neural cell bodies and in glial cell processes.6.6. Neurons and glial cells contain numerous inclusions of complex internal structure.
1.1. An in vitro test is described for assaying tissue extracts for “metabolic hormone” in Pila ovata using oxygen uptake in muscle slices.2.2. Extracts of ganglia, kidney and liver in Ringer stimulate oxygen uptake in muscle slices.3.3. Oxygen uptake is also stimulated by serotonin, some indole amines, some amines and adrenaline.4.4. The factor in the liver is non-dialysable, heat stable, extractable in 95% acetone and partly soluble in chloroform. Evidence is given to suggest that the majority of the activity of the liver is not due to serotonin or tryptamine. The possibility of a steroid is raised.5.5. An active factor is also present in the livers of two bilharzia vectors. The possible significance of this is discussed.
1.1. The titrimetric method of Glick (1937) was used to measure cholinesterase activity in various tissues of Helix aspersa.2.2. Such activity was found in a variety of tissues and was particularly high in the heart.3.3. The activity showed some of the properties of a true cholinesterase.
Welsh and Moorhead1 found large amounts of 5-hydroxytryptamie (5-HT) in the nervous system of different classes of molluscs and postulated its possible role as a transmitter. More recently the presence of 5-HT in land-snail nervous tissue was confirmed by Kerkut and Cottrell2 and by Cardot and Ripplinger3. The interest of this finding was stressed by Ersparmer4, who pointed out that ``a thorough study of the 5-HT in the nervous tissue of Molluscs may offer a key to a better understanding of the function of the amine in the brain of Vertebrates''.
1. 1. Density gradient fractions of Mercenaria ganglia homogenate with high relative specific activities of 5-hydroxytryptamine (5-HT) and also containing some Susbtance X (a potent cardioexcitor) were examined under the electron microscope. 2. 2. An attempt was made to correlate the occurence of the different types of small particles observed in different fractions with the relative specific activities of 5-HT and Substance X, in order to determine the types of particles with which the substance are normally associated. 3. 3. Results indicated that Substance X is associated with "uniformly granulated vesicles" of 1000-3000 Å dia. 4. 4. 5-HT is probably not associated with electron dense-cored particles (1000-2000 Å dia). The precise subcellular localization of 5-HT in molluscan nervous tissues is briefly discussed in the light of observations made.
1.1. The dopamine (DA) and 5-hydroxytryptamine (5-HT) contents of the ganglia of Mercenaria mercenaria expressed as ng. per ganglion were as follows: View Within Article1.2. Pedal ganglia synthesize [14C]DA from [14C]tyrosine but do not form significant amounts of [14C]noradrenaline (NA). [14C]5-HT is also formed from [14C]tryptophan in pedal ganglia.2.3. Incubation of pedal ganglia in KCl-rich sea water accelerates synthesis of [14C]DA from [14C]tyrosine two- to threefold compared with controls. The specific activity of DA isolated from the K+-stimulation ganglia is corresponding increased.3.4. The acceleration of DA synthesis appears to take place at the tyrosine hydroxylation step.4.5. Synthesis of DA from tyrosine in pedal ganglia is inhibited up to 60 per cent by 10−4M DA in the medium.
All nervous systems are subject to neuromodulation. Neuromodulators can be delivered as local hormones, as cotransmitters in projection neurons, and through the general circulation. Because neuromodulators can transform the intrinsic firing properties of circuit neurons and alter effective synaptic strength, neuromodulatory substances reconfigure neuronal circuits, often massively altering their output. Thus, the anatomical connectome provides a minimal structure and the neuromodulatory environment constructs and specifies the functional circuits that give rise to behavior.
Microchromatography of dansylated substances was used to estimate the serotonin content of a giant serotonin-containing neuron situated in the metacerebral ganglia of Helix pomatia. Perfusion of the central nervous system of this snail with 14C-5-HTP showed that the giant serotonin-containing neuron can use this precursor to form 14C-serotonin, whereas a non-amine containing cell can not. The significance of these results is discussed. © 1972 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.
1.1. Acetylcholine can hyperpolarize certain snail neurones and inhibit the action potentials.2.2. The spontaneous inhibitory post-synaptic potentials (ipsp) have a different reversal potential to that for acetylcholine.3.3. The ipsp is less sensitive than the acetylcholine response to chloride changes.4.4. The possible relationship between the ipsp and acetylcholine is discussed.
1.1. Intracellular recordings were made from a single identifiable neuron in the brain of the snail Helix aspersa.2.2. Two epsps could be recorded from this cell following nerve stimulation. Stimulation of the left pallial nerve elicited an epsp with a slow rise-time and long duration. Stimulation of the anal nerve elicited an epsp with a fast rise-time and short duration.3.3. Neuropharmacological evidence suggests that presynaptic release of 5-HT is responsible for the slow epsp while release of acetylcholine is responsible for the fast epsp.4.4. Pretreatment of snails with hemicholinium reduces the size of the fast epsp while having no effect on the slow epsp. Pretreatment with reserpine, p-chlorophenylalanine, or α-methyl-5-hydroxytryptophan reduces the size of the slow epsp, while pretreatment with 5-hydroxytryptophan slightly increases the size of the slow epsp.5.5. It is concluded that the slow epsp is due to 5-HT and the fast epsp to acetylcholine.
The sections in this article are:
1.
Rhythmic activity of the isolated penial complex of the freshwater snail Limnaea stagnalis is described.
2.
The preparation responds to acetylcholine, adrenaline, 5-HT and GABA, and the significance of these results is discussed.
3.
The results show marked differences from those obtained with a similar preparation from a stylommatophoran pulmonate.
1.
Die rhythmische Aktivitt des isolierten Penis-Komplexes der Wasserschnecke Limnaea stagnalis wird beschrieben.
2.
Das Prparat antwortet auf Acetylcholin, Adrenalin, 5-HT und GABA; die Bedeutung dieser Ergebnisse wird diskutiert.
3.
Die Ergebnisse zeigen deutliche Unterschiede zu jenen, die an einem hnlichen Prparat von einem stylommatophoren Pulmonaten erzielt wurden.
Acetylcholinesterase (AChE) activity in the central nervous system and foot muscle in the garden snail,Cryptozona ligulata, was maximum at 20.00 h and minimum at 08.00 h during the 24 h period of the day. The cyclic variation in acetylcholine (ACh) was out of phase with that of AChE. In the body fluid, ACh content showed a rhythm with maximum at 00.00 h and minimum at 12.00 h, with AChE activity being in phase with it.
The rhythm of spontaneous electrical activity of the nervous system was in phase with that of AChE activity in tissues. Perfusion with body fluid collected from snails at 20.00 h elevated the spontaneous electrical activity, while body fluid collected at 08.00 h inhibited the activity. Perfusion with extract prepared from the central nervous tissue isolated at 08.00 h elevated the electrical activity, while the extract prepared from nervous tissue isolated at 20.00 h inhibited the activity. Perfusion with 10−4 M acetylcholine chloride solution elevated the electrical activity.
It is suggested that the synthesis and release of ACh occur in a regular diel cycle in tissues. These changes, among others, may be responsible for the observed diurnal rhythmicity in electrical activity in the snail.
The concentrations of -phenylethylamine,p-tyramine,m-tyramine,m-octopamine and tryptamine in the ganglia or foot muscle ofHelix aspersa range from p-Octopamine levels are higher in ganglia (327 ng/g) than in foot muscle (4.1 ng/g). Dopamine and 5-hydroxytryptamine range from 840 to 2710 ng/g while their acid metabolites, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid and 5-hydroxyindoleacetic acid range from
1.
Gel filtration of tissue homogenates fromHelix aspersa separates cardioactive agents into four peaks of activity. One peak inhibits an isolated heart ofHelix, the remaining three are excitatory.
2.
Elution characteristics, enzymatic sensitivity, and pharmacological properties indicate that the active principle of the inhibitory peak is acetylcholine, while that of one of the excitatory peaks is 5-hydroxy-tryptamine.
3.
The two remaining peaks lose their activity when incubated with Pronase, trypsin, or chymotrypsin. This indicates that the active substances in these peaks are peptides.
4.
The active substance of one of these peaks has an apparent molecular weight of ca. 700, and has been termed small cardioactive peptide(s) (SCP). Its presence is essentially confined to the nervous system and it does not appear to play a physiological role in control of the heart.
5.
The other peptide cardioexcitor had an apparent molecular weight of ca. 7000, and was termed large cardioactive peptide(s), (LCP). It is found primarily in the sub-esophageal ganglia, several nerve trunks, the hemolymph, and in particularly high concentrations in the auricle.
6.
Kinetic and pharmacological results suggest that LCP uses a different receptor in theHelix heart than does 5-HT.
7.
It was concluded that LCP demonstrates several of the characteristics expected of a cardioactive neurohormone.
Spontaneous unit discharges (SUD) were recorded simultaneously from the VMH and lateral area (LH) of the hypothalamus in cats by glass capillary electrodes. Effects of ether anesthesia and electrical stimulation of the LH and VMH structures on the activity of the VMH and LH alone and the reciprocal relation between them were determined. Distributions of SUD frequencies and interspike intervals were determined, and after the stationarity of the time series had been established, auto and cross-correlation functions were calculated. Results on the intimate reciprocal relation between the VMH and LH fit the predictions of a stochastic model quite well and were also confirmed by changes in the EEG recorded from both hypothalamic regions in chronic twelve-hour food deprived animals.
1.1. Cholinesterase activity in snail brain extracts was investigated by spectrophotometry, partial purification and disc electrophoresis.2.2. Snail brain cholinesterase showed substrate inhibition at 4 mM, was inhibited by eserine 10−6M, activated by cations and had a pH optimum of 8·4.3.3. The cholinesterase obtained by partial purification of the brain extracts gives only one band with esterase activity when further separated by electrophoresis.4.4. An attempt at determining the molecular weight of the constituent polypeptide of the snail brain cholinesterase is described. Four polypeptides were found, their total molecular weight was 2·4 x 105.5.5. It is suggested that the cholinesterase found in snail brain is a true acetylcholinesterase (E.C. 3.1.1.7).
1. There is seasonal variation in the 5HT level of the central nervous system and heart of the snail, Helic pomatia L.: in active animals the 5HT content is higher in the cerebral ganglia, auricle, and ventricle in the autumn than at spring, while this pattern is reversed in the suboesophageal ganglion.2. Snails kept in dry conditions at room temperature fall into a state of rest. Under such conditions an increase of the 5HT level was observed in the C.N.S. and heart both in the summer as well as in the winter; the question remains as to what results from the decrease of the 5HT utilization during the resting state of the animal.3. There is a different seasonal variation of the 5HT level in snails kept in a refrigerator: during the first winter months the 5HT level of the ganglia increases; this is followed by a decrease, while in the summer an initial decrease with subsequent increase is observed. The 5HT content of the heart showed an initial decrease both during the winter and the summer.4. Arousal of the snails from hibernation in winter causes a decrease of the serotonin level of the ganglia. On cooling these animals again, the 5HT level increases only to a moderate degree.5. The variations of the 5HT level in snails can be considered partly as the consequence of the change of the activity, but on the other hand the serotonin level can play a role in the determination of the activity of the animal.
1.1. The action of eserine and two organophosphorous cholinesterase inhibitors on the sensitivity of identified neurones of Lymnaea stagnalis and Planorbarius corneus to cholinergic agonists was studied with microelectrodes.2.2. Eserine did not affect the action of ACh on Lymnaea neurones but did enhance the depolarizing potency of BuChE substrates, BuCh and D-6, as much as 1·6-fold and 13-fold respectively.3.3. On Lymnaea neurones the BuChE selective inhibitor, compound GT-165, potentiated D-6, BuCh, ACh and AChE substrate, acetyl-β-methylcholine (mecholyl), as much as 33·8-, 3·7-, 4- and 3·2-fold respectively. The selective inhibitor of AChE, compound Gd-42, increased the action of ACh 6·9 times and that of mecholyl four times, but did not change the D-6 and BuCh depolarization.4.4. From these findings a conclusion may be drawn about high cholinesterase activity in Lymnaea ganglia; there seems to exist at least two different enzymes. This was emphasized by the data of experiments with a consecutive application of Gd-42 and GT-165.5.5. With the inhibitors used we failed to reveal any essential cholinesterase activity in Planorbarius ganglia.
1.1. Monoamine oxidase [monoamine: oxidoreductase (deaminating); EC 1.4.3.4; MAO] has been studied in homogenates of adult Schistosoma mansoni.2.2. Male worms had a much higher specific enzymic activity than females.3.3. Tryptamine (KmμM) was deaminated five times as fast as serotonin (Km 45 μM).4.4. General characteristics (pH optima, subcellular distribution, affinity for substrates and for “typical” MAO inhibitors)_were indistinguishable from those of mammalian MAO.5.5. Evidence from thermal inactivation, differences in sensitivity to inhibitors and cross-inhibitors by substates suggests that there is more than one MAO in schistosomes.
1.1. Sialic acid is widely distributed in glycoconjugates in vertebrates (sialoglycoproteins and sialoglycolipids).2.2. The lack of sialic acid as glycoconjugate in Mollusca Gastropoda led us to investigate if it might be replaced by a similar C9 acidic glycoconjugate.3.3. The presence of muramic acid in Mollusca Gastropoda suggests that it might substitute sialic acid, at least in muramyl-glycoproteins in this group.
The influence of the subtances acetylcholine, dopamine and serotonin, normally present in the central nervous system of molluscs, were studied either after iontophoretic application or after perfusion. A survey is given of investigated neurons in the parietal and the viscera' ganglia according to their membrane responses. These data have been discussed in relation to observed postsynaptic potentials. An attempt is made to classify the neurons pharmacologically according to conventions of other authors. It was found thereby that some neurons having EPSP's were not depolarized by any of these substances, while some others having IPSP's were not hyperpolarized by them.
1. Biochemical and histochemical analysis of the circumesophageal ganglia of the nudibranch mollusc Hermissenda crassicornis revealed four putative neurotransmitters: acetylcholine, dopamine, serotonin and histamine.2. Acetylcholine was synthesized and accumulated within the neuropile where all known synaptic interactions occur.3. Histochemical staining demonstrated that acetylcholinesterase is almost entirely localized in the neuropile region.4. Degradation of ACh was increased by perfusing the preparation with seawater containing high K+.5. Study of the enzymes involved in the metabolism of the above-mentioned neurotransmitters revealed that choline-acetyltransferase had much higher specific activity than either tyrosine or tryptophan hydroxylases.6. The temperature optimum found for the CAT was 20°C, while tryptophan and tyrosine hydroxylase showed an increase in their activity up to 30 and 35°C respectively.7. AChE was found to have high activity throughout the temperature range tested (0–35°C).
The chromatogrammed brain extract is shown to have two components that act on the retractor pharangeal muscle of the snail. One component causes the muscle to relax; this is most probably 5 HT. The other component causes the muscle to contract; this component is not acetylcholine.
1.1. Acetone-water extracts from various snail tissues, such as the brain, mantle, foot, mid-gut and heart, have a cardiac accelerating property. The chromatographic purification of this substance shows that it differs in properties from 5HT.2.2. The differences between the cardiac accelerator and 5HT are1.(a) The extract action is not antagonized by LSD.2.(b) The winter frog heart and the summer grog heart are both accelerated by the extract whilst 5HT inhibits the winter frog heart and accelerates the summer frog heart.3.(c) Solutions of extract and 5HT show reactions to chemical tests.4.(d) The extract and 5HT have a different Rf in tert. butanol-methanol-water.5.(e) The addition of 5HT to the heart causes an acceleration whilst the extract causes an accelaration and a regularization of the beat.1.3. It is suggested that the active principle in the extract is an aromatic amine possessing one or more hydroxyl groups, one of which is possibly in the 5 posititions. It does not appear to be an indole.
1.1. The connexions between some cell bodies and the peripheral nerves in the ganglia of Helix aspersa are described.2.2. The responses of the nerve cells to chemicals (acetylcholine, histamine, 5HT, 5HTP, dopamine, glutamic acid, GABA, phenylalanine and β-alanine) were tested.3.3. Eighteen identified cells gave consistent selective responses to the chemicals. Some were sensitive to acetylcholine, others to 5HT, or histamine, or dopamine.4.4. Helix brain contains material which when chromatogrammed can excite or inhibit nerve action.
1.1. The amino acid content of the serum of the snail Helix aspersa is 1 μM/ml serum. The content for brain tissue is 18.2 μM/g wet weight.2.2. The most common amino acid in the blood was alanine and this was closely followed by glutamine. The others in order of decreasing conentration were serine, glycine, glutamic acid, valine, threonine, leucine, aspartic acid, cysteic and arginine. Traces were found of tyrosine, α-amono-n-butyric acid, proline and histidine.3.3. The most common amino acids in the brain were glutamic acid, alanine and lysine. The others in order of decreasing concentration were glutamine. cysteic, serine, glycine, leucine, threonine, valine and asparctic acid, and traces of tyrosine, histidine, cystine and methionine.4.4. Other amino acids appeared in hydrolysed brain extracts. These were n-methyl histidine, γ-amino-butyric acid, cysteine, methionine, proline, and traces of isoleucine, isoasparagine and diamino caproic acid.
1.1. The action of drugs on the perfused isolated ventricle of the snail Strophocheilos o oblongus is described.2.2. ACh has an excitatory action on the heart.3.3. An antagonism between ACh-atropine was found in the heart.4.4. The cardio-accelerator present in Strophocheilos heart tissue extract is not ACh.
1.(1) The effect of adding various chemicals to the isolated brain of the snail Helix aspersa is described. The reactions were followed by measuring the effect of the chemicals on the resting potential and the spontaneous action potentials of the nerve cells.2.(2) All the following chemicals were effective at dilutions between 10−7 and 10−11 g/ml. The sign indicates their overall acceleratory (+) or inhibitory (−) effect on the spontaneous activity. View Within Article3.(3) Dopamine and phenylalanine caused a hyperpolarization of the resting potential.4.(4) Phenylalanine, glutamic acid and cocarboxylase could protect the cell against the action of high concentrations of acetylcholine.5.(5) It is thought that most of the above chemicals may occur naturally in the snail and that acetylcholine and dopamine are the most likely transmitter substances.6.(6) Most of the drugs had a dual action; inhibiting some cells and accelerating others. It is suggested that there is a marked chemical heterogeneity in the CNS with cells reacting specifically but different to a given chemical.
Action de la 5-hydroxytryptamine chez les c6phalopodes
- Z M Fisctter
- P Gnlr~
}~.,,ce Z. M., FISCttER P. & GnlR~:'rTl F. (1952) Action de la 5-hydroxytryptamine chez les c6phalopodes. Arch. Int. Physiol. 60, 165-171.
Recherches sur la composition en amino acids libres du systdme nervcux d'Helix pomatia
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- Inger J
CAm)OT J. & IOPm.INGER J. (1961) Recherches sur la composition en amino acids libres du systdme nervcux d'Helix pomatia. C.R. Soc. Biol., Paris 155, 1961-1963.
Nouvelles observations sur la production d'une substance équivante a l'acétyl choline par le coeur d'Helix pomatia en fonction de la tension de l'organe et de la concentration du milieu de perfusion
- Jullien
JULLIEN A., RIPPLINCER J. & MERCIER J. (1953) Nouvelles observations sur la production d'une substance 6quivante a l'ac6tyl choline par le coeur d'Helix pomatia en fonction de la tension de l'organe et de la concentration du milieu de perfusion. J. Physiol. Path. C,~n. 45, 140-145.
Neuropharmacology of the pharyngeal retractor muscle of the snail Helix aspersa
- Kf Ut
KF.m;UT G. A. & COTT~I.L G. A. (1962b) Neuropharmacology of the pharyngeal retractor muscle of the snail Helix aspersa. Life Science 1,229-31.
The specific chemical sensitivity of Helix nerve cells Untersuchungen zur Storung der Herztatigkeit beim Helix pomatia
- Wai Ker
KERKUT G. A. & WAI.KER R. J. (1962) The specific chemical sensitivity of Helix nerve cells. Comp. Biochem. Physiol. 7, 277-288. MENG K. (1960) Untersuchungen zur Storung der Herztatigkeit beim Helix pomatia. Zool. Jber. 68, 539-566.
Chromatographic and Electrophoretic Techniques Effect inhibiteur ou excitateur du chlorure d'acdtyl-choline sur le neurone d'Escargot
- Heinemann
- London
- C L Tal
- Ge~citf
- Nfeld H
Exp. Biol. 17, 96-115. SMITH I. (1960)Chromatographic and Electrophoretic Techniques. Heinemann, London. TAL'C L. & GE~CItF.NFELD H. (1960) Effect inhibiteur ou excitateur du chlorure d'acdtyl-choline sur le neurone d'Escargot. J. Physiol. Path. G~n. 52, 236-236.
Serotonin as a possible neurohumoral agent
- Welsh
A nerve muscle preparation from the snail
- Ramsay
Les esters de la choline dans les extraits de tissues des invertébrés
- Bacq
Recherches sur la composition en amino acids libres du systéme nerveux d' Helix pomatia
- Cardot
Libération d'acétylcholine par l'excitation du nerf cardiaque chez Helix pomatia
- Jullien