DC-magnetoencephalography (DC-MEG) technique has been refined and allows to record cortical activity in the infraslow frequency range less than 0.1 Hz noninvasively. Important questions however, remained, especially, how specific these infraslow activations can be recorded and whether different activations, for example, motor versus acoustic, can be separated. To clarify these questions, in the present DC-MEG study, cortical infraslow activity was investigated intraindividually in response to different activation modalities, that is, motor versus acoustic: in 13 individuals, 30-s periods of finger movement or listening to concert music, were interleaved for 60 min. DC-MEG was capable to resolve intermodal differences concerning the relative amplitudes, field patterns, and source localizations. These results clarify that DC-MEG allows to identify and to discriminate modality-specific infraslow cortical neuronal signals.
The auditory processing of physical stimulus features can be measured by the mismatch negativity. Past studies have shown that higher-order stimulus features also elicit a mismatch negativity. In some studies, a second component, termed late mismatch negativity, has been observed; yet the functional significance of this component remains unclear. We tested two-tone-pattern stimuli following an abstract rule in healthy adults. As expected, the tone pattern elicited a significant mismatch negativity peaking at 146 ms but a significant late mismatch negativity at around 340 ms was also observed. These findings show that the violation of an abstract rule elicits an early and late mismatch negativity. The late mismatch negativity might be triggered on the basis of auditory rule extraction processes and reflect a transfer of rules to the long-term memory.
The large-conductance Ca(2+)-dependent K+ channels or BK channels in cerebellar granule cells were studied by patch-clamp technique, and the effects on channel activity of the molecule NS 004 (1-(2-hydroxy-5-chlorophenyl)-5-trifluoromethyl-2- benzimidazolone) were investigated. The channels had a unit conductance of 187 pS, were blocked by charybdotoxin and activated by internal Ca2+. NS 004 (10-30 microM) significantly increased the single channel opening frequency as well as the mean open time. In whole-cell recordings the compound shifted the BK current-voltage relationship by up to 40 mV towards negative membrane potentials. NS 004 is an efficient BK channel opener, which may represent a novel approach to relaxation of neuronal cells expressing this type of K+ channel.
Pain is the most common symptom reported in both the general population and the general medical setting. The aim of this study is to evaluate the effectiveness, tolerance, and safety of venlafaxine extended-release (XR) monotherapy in treating first-episode outpatients fulfilling the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV) criteria for major depressive disorder with associated painful physical symptoms. Of the 102 outpatients enrolled, 86 (84.3%) completed the study. Venlafaxine XR treatment (75-225 mg/day) was followed by a significant decrease in the total scores for the 17-item Hamilton Depression Rating Scale from baseline to the second weekend (t value=16.12, P<0.0001) and at every subsequent visit (weeks 4, 6, and 8, all P<0.0001). Significant differences were also found in the mean Visual Analog Scales for overall pain and the mean medical outcomes study pain measures from baseline to the second weekend (t value=14.99, P<0.0001; t value=12.59, P<0.0001) and at every visit (all P<0.0001). At the end of the eighth week, venlafaxine XR achieved response and remission rates of 68.6 and 40.2%, respectively. The remission rate for pain responders (improvement in Visual Analog Scale overall pain from baseline to last observation ≥50%) was significantly greater than that for pain nonresponders (56.1 vs. 20.0%, P<0.0001). The most common (≥10%) adverse events were nausea (31.4%), dizziness (26.5%), and somnolence (22.5%). Venlafaxine XR is possibly an effective and safe option in the treatment of depression and associated painful physical symptoms.
T-type voltage-dependent calcium channels may play an important role in synaptic plasticity, but lack of specific antagonists has hampered investigation into this possible function. We investigated the role of the T-type channel in a canonical model of in-vivo cortical plasticity triggered by monocular deprivation. We identified a compound (TTA-I1) with subnanomolar potency in standard voltage clamp assays and high selectivity for the T-type channel. When infused intracortically, TTA-I1 reduced cortical plasticity triggered by monocular deprivation while preserving normal visual response properties. These results show that the T-type calcium channel plays a central role in cortical plasticity.
Using K+ phosphate buffer with 25 nM spiperone, [3H]YM-09151-2 binding showed a high affinity for sigma receptors but no affinity for D2 dopamine or 5-HT1A receptors in rat brain. The order of pKi values of various sigma compounds at [3H]YM-09151-2 binding sites and stereoisomer selectivity were consistent with previous studies using other sigma ligands such as (+)-[3H]SKF-10047, [3H]DTG and (+)-[3H]3-PPP. Although Scatchard analysis fitted a one-site model, competition between [3H]YM-09151-2 and (+)-pentazocine revealed two sites, sigma 1 and sigma 2 receptors, at which the Ki values of YM-09151-2 were 8.4 nM and 9.6nM, respectively. Autoradiography using [3H]YM-09151-2 also showed a characteristic distribution of sigma receptors in rat brain. [3H]YM-09151-2 is, therefore, a potent and useful radioligand for sigma 1/sigma 2 receptor subtypes.
The possible neuroprotective role of a novel and highly selective cyclooxygenase-2 inhibitor GW637185X was studied in a model of acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced injury of nigrostriatal dopaminergic (DA) neurons in the mouse. Stereological and microdensitometrical analysis of nigral tyrosine hydroxylase-immunoreactive cell bodies and striatal tyrosine hydroxylase-immunoreactive terminals, respectively, showed that GW637185X exerted a full protection against MPTP-induced degeneration of the nigro-striatal pathway. In contrast to earlier studies, these findings demonstrate that acute inhibition of cyclooxygenase-2 can result in a full neuroprotective effect not only on nigral DA cell bodies, but also on striatal DA terminals in the mouse MPTP model.
Defects in complex I and alpha-ketoglutarate dehydrogenase (alpha-KGDH) occur in the substantia nigra in Parkinson's disease (PD). Isoquinoline derivatives structurally related to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP+) are implicated in the cause of PD as endogenous toxins and are inhibitors of complex I. However, their effects on alpha-KGDH and other mitochondrial non-respiratory chain enzymes are unknown. We have examined the effects of six isoquinoline derivatives (isoquinoline, N-methylisoquinolinium, N-n-propylisoquinolinium, 1,2,3,4-tetrahydroisoquinoline, N-methyl-1,2,3,4-tetrahydroisoquinoline and salsolinol) and MPP+ on the activities of alpha-KGDH, citrate synthase (CS) and glutamate dehydrogenase (GDH) in mitochondrial fragments from rat forebrain. None of the compounds examined had any effect on CS or GDH activity. In contrast, all isoquinoline derivatives investigated and MPP+ inhibited alpha-KGDH activity in a concentration-dependent manner with IC50s ranging from 2.0 to 18.9 mM. MPP+ was previously shown to inhibit alpha-KGDH, but this is the first report of inhibition of alpha-KGDH by isoquinoline derivatives. These findings may represent an additional mechanism contributing to mitochondrial dysfunction and cell death in Parkinson's disease.
Glial cell line-derived neurotrophic factor (GDNF) has significant therapeutic potentials, in particular for neurodegenerative disorders. To determine factors that would enhance GDNF expression, we analysed the effect of 1,25-(OH)2 D3 in C6 glioma cells. Treatment of C6 cells with 10(-7) M, 1,25-(OH)2 D3 for 48 h elicited an 18.5-fold increase in the level of GDNF mRNA. In addition, our results indicate that 1,25-(OH)2 D3 is effective at concentrations as low as 10(-10) M and that retinoic acid has additive effects. These data indicate that 1,25-(OH)2 D3 is a potent inducer of GDNF expression and suggest that 1,25-(OH)2 D3 may contribute to the regulation of GDNF in vivo.
The effect of 1,25-dihydroxyvitamin D3 on neurotrophin mRNA expression was studied in primary cultures of astrocytes. In addition to its known effects on NGF expression, 1,25-dihydroxyvitamin D3 was shown to upregulate NT-3 mRNA levels, while NT-4 expression was slightly but significantly downregulated. No effect was observed on BDNF mRNA expression. These data clearly show a differential regulation of the four neurotrophins by 1,25-dihydroxyvitamin D3 in primary cultures of astrocytes and suggest that 1,25-dihydroxyvitamin D3 may participate in the expression of NGF, NT-3 and NT-4 in the central nervous system.
In the rat central nervous system (CNS), inositol 1,4,5-trisphosphate receptor (IP3R) type 3 was immunolocalized with a type 3-specific monoclonal antibody (mAb). The protein was expressed principally in prototype astrocytes, ependymal cells around the ventricle, and Bergmann glial cells in the cerebellum. These cells were stained by antibody against glial fibrillary acidic protein (GFAP), indicating the coexistence of GFAP and IP3R type 3. Immunoblot analysis using a brain homogenate detected a 240 kDa protein, verifying that the observed immunoreactivity is from the IP3R type 3 protein. IP3R type 1 and type 2 were not detected immunohistochemically in astrocytes. These results suggest that IP3-induced CA2+ release (IICR) in astroglia is directed by IP3R type 3, whereas IICR in neuronal cells is mediated by IP3R type 1.
The mouse fructose-1,6-bisphosphatase (FBPase) cDNA was previously cloned from testicular teratocarcinoma cultured cells (F9 cells). Using this published nucleotide sequence four primer sets were defined and used to amplify FBPase transcript from cerebral cortex, heart, kidney, liver and testis of male C57B1/6 mice. Only one primer set was efficient in all total RNA prepared from the various tissues. The restriction maps of these RNA amplification products suggested the existence of three different FBPase transcripts; this was confirmed by the nucleotide sequences of the FBPase transcripts and by the deduced amino acid sequences. These data are consistent with the existence of three different FBPase genes. This may be relevant in neurological disease in which abnormalities of brain glucose metabolism are involved.
Modification of sodium channel availability and behavior is obviously a good candidate for alteration of action potential observed during aging. In the present study, we revealed age-related alterations in the expression of voltage-gated Na+ (Na(v)) channel in rat cerebellum by immunohistochemistry. In the cerebellar cortex of aged rats, Na(v)1.1 immunoreactivity in Purkinje cell bodies was highly increased, whereas granule cells showed lower staining intensity. In the cerebellar nuclei of aged rats, Na(v)1.1 and Na(v)1.2 expression was specifically increased in the cerebellar output neurons, which was confirmed by image analysis. The first demonstration of age-related changes in Na(v) channel expression contributes to our understanding of the mechanisms responsible for alteration in synaptic transmission during aging.
Focal cortical dysplasia (FCD) is one of the causes of intractable epilepsy in humans. Cytomegalic neurons, not balloon cells, are considered to be the putative generators of epileptic activity in FCD type IIb (FCDIIb). Voltage-gated sodium channel III α-isoforms (Nav1.3) play crucial roles in the initiation and propagation of action potentials and are important regulators of neuronal excitability. Here, we examined 12 FCDIIb surgical specimens from patients undergoing surgery for epilepsy and used age-matched normal control cortical tissue (CTX) from 10 autopsy samples as controls. Using reverse transcription-PCR and western blot techniques, we found that the mRNA and protein levels of Nav1.3 were clearly upregulated in FCDIIb surgical specimens compared with the controls (CTX). Results of immunohistochemistry analyses demonstrated that Nav1.3 immunoreactivity was widely present in FCDIIb lesion tissue; specifically, high levels of Nav1.3 immunoreactive proteins were located mainly in cytomegalic neurons of different sizes and shapes, not in balloon cells. Double-labeling studies showed most cytomegalic neurons expressing Nav1.3 colabeled with neuronal markers and glutamate receptors-1. Taken together, our results show an upregulation of Nav1.3 protein and a specific cellular distribution of Nav1.3 proteins in FCDIIb lesion tissue samples, suggesting that Nav1.3 may be involved in the generation of epileptic activity in FCDIIb.
The tetrodotoxin-resistant voltage-gated sodium channel Nav 1.8 is expressed only in nociceptive sensory neurons. This channel has been proposed to contribute significantly to the sensitization of primary sensory neurons after injury. We have studied the nociceptive behaviours of mice carrying a null mutation in the Nav 1.8 gene (Nav 1.8 -/-) in models of peripheral inflammation as well as a model of neuropathic pain. The results from the present studies reveal that Nav 1.8 is a necessary mediator of NGF-induced thermal hyperalgesia but is not essential for PGE2-evoked hypersensitivity. Neuropathic pain behaviours were unchanged in Nav 1.8 -/- mice indicating that this channel is not involved in the alteration of sensory thresholds following peripheral nerve injury.
The NMDA antagonist CGX-1007 (Conantokin-G) has previously been shown to possess potent neuroprotective properties when administered intracranially following experimental ischemic brain injury. Using the same model of middle cerebral artery occlusion (MCAo) in rats we now report the neuroprotective effects of CGX-1007 when delivered intrathecally (i.t.). When given 4 h post-occlusion, a reduction in brain infarction was measured along with significant neurological recovery. Furthermore, we describe an i.t. neuroprotective therapeutic window lasting > or = 8 h from the start of the injury. Critically, this is the first comprehensive report of a neuroprotective agent that can be administered i.t. to ameliorate experimental brain injury and potentially provide an excellent therapeutic window as a neuroprotection treatment.
S-100 beta, which is capable of exerting neurotrophic effects on cultured neurones and promoting the survival of motor neurones in vivo, has recently been found in distinct neurones of the rat hindbrain. Here we report that S-100 beta, as well as being present in satellite and Schwann cells, is also present in neurones of sensory ganglia (dorsal root ganglion, trigeminal, petrosal, jugular and nodose ganglia) but absent from neurones of the superior cervical ganglion. In the sensory ganglia, many neurones were immunoreactive, while the staining intensity varied among the neurones. Neuronal S-100 beta appeared in developing rats as early as postnatal day 1. No immunoreactive neurones were observed in the superior cervical ganglion during development. The results are suggestive of selective neurotrophic effects of S-100 beta.
The brain peptide cholecystokinin (CCK) has been shown to counteract the analgesic effects of morphine suggesting a physiological antagonism between opioid and CCK neural systems. This has been definitely demonstrated in this study by co-administration of the CCK-B selective antagonist L-365,260 with RB 101, a systemically active inhibitor of peptidases, which fully protects the endogenous opioids, the enkephalins, from their inactivation. The naloxone reversible analgesic effects induced by RB 101 in the mouse hot-plate and rat tail-flick tests were strongly increased by low doses of L-365,260. These results could have important clinical applications by reducing the efficient dose of RB 101, which has recently been shown to be practically devoid of morphine-like side-effects.
The effects of huperzine A on memory impairments induced by scopolamine were evaluated using a radial maze task and inhibition of cholinesterase in vitro compared with the effects of E2020 and tacrine. Scopolamine (0.2 mg kg-1) significantly impaired spatial memory in rats. Huperzine A (0.1-0.4 mg kg-1, p.o.), E2020 (0.5-1.0 mg kg-1, p.o.) and tacrine (1.0-2.0 mg kg-1, p.o.) could reverse these scopolamine-induced memory deficits. The ratios of huperzine A, E2020 and tacrine for butyrylcholinesterase:acetylcholinesterase determined by a colourimetric method were 884.57, 489.05, and 0.80, respectively. The results demonstrated that huperzine A was the most selective acetylcholinterase inhibitor, and improved the working memory deficit induced by scopolamine significantly better than did E2020 or tacrine, suggesting it may be a promising agent for clinical therapy of cognitive impairment in patients with Alzheimer's Disease.
The effect of topical application of interleukin 2 (IL-2) on afferent sensory transmission to the neurones in the primary somatosensory (SI) cortex was determined quantitatively in anaesthetized rats. IL-2 (0.1, 1.0, 5.0 units) significantly suppressed afferent sensory transmission in SI cortical neurones (n = 19) in a dose-dependent manner. IL-2-induced suppression fully recovered by 60 min after drug. In control experiments, saline solution containing 0.2% bovine serum albumin, used as a vehicle, did not affect afferent sensory transmission. Our results suggest that IL-2 and its receptor present in the SI cortex may be involved in the processing of afferent sensory information.
The contribution of vasodilator cyclooxygenase (COX) metabolites to the maintenance of the cerebrocortical blood flow (CBF) has been studied under physiological conditions and in nitric oxide (NO) deficiency. Inhibition of COX decreased resting CBF without changing arterial blood pressure. NO synthase blockade resulted in hypertension and CBF reduction as well as in enhanced cerebral prostacyclin and prostaglandin E2 production. Despite the increased vasodilator prostanoid release in the absence of NO, the CBF-decreasing effect of COX blockade failed to increase. Therefore, the COX pathway seems to play a similar role under physiological and NO-deficient conditions in the maintenance of the resting CBF.
Nitroglycerin, which may be regarded as a prodrug for nitric oxide, induces a mild to moderate headache in healthy subjects. In order to study whether migraine patients are more sensitive to nitric oxide than non-migrainous subjects, four different doses of intravenous nitroglycerin were given in a double blind design to 17 migraine patients, 17 age and sex matched healthy controls and 9 subjects with tension-type headache. The nitroglycerin-induced headache was significantly more severe in migraine sufferers, lasted longer and fulfilled diagnostic criteria for migraine more often. We have previously shown a similar supersensitivity to histamine which in human cerebral arteries activates endothelial H1 receptors and causes endothelial production of nitric oxide. Migraine patients are thus supersensitive to exogenous nitric oxide from nitroglycerin as well as to endothelially produced nitric oxide. It is suggested that nitric oxide may be partially or completely responsible for migraine pain.
The serotonin hypothesis in schizophrenia had regained interest with the superior efficacy of clozapine in the refractory schizophrenic patients. Among the serotonin receptors, the serotonin 2A (5HT2A) receptor subtype is the most widely studied. Previous studies on the association between a silent mutation polymorphism of the 5HT2A gene (102T/C) and schizophrenia or clozapine response have yielded conflicting findings. Therefore, we investigated whether these genetic variants of the 5HT2A receptor are associated with schizophrenia or with response to clozapine treatment in a Chinese population. Ninety-seven schizophrenic patients and 101 control subjects were included in the study. The receptor variants were found at similar frequencies in schizophrenic patients and healthy control subjects. Also, we did not find the variants to influence the response to clozapine in schizophrenic patients. We suggest that the assessment method of clozapine response and the ethnicity may influence the result.
Hyperactivity of the dopaminergic system and a hypoglutamatergic state have been hypothesized to underlie schizophrenia. It has also been proposed that neuroleptics may interact not only with the dopaminergic system but also with the glutamatergic system. We found that daily intraperitoneal injections of haloperidol (1 mg kg-1) for 21 days resulted in increased binding (10-20%) to the NMDA type of glutamate receptors in the outer layers of rat parietal cortex. Quantitative receptor autoradiography indicates that the action of haloperidol is regionally specific since no changes in NMDA receptors were found in the hippocampus and thalamus. Our data suggest that haloperidol may exert its antipsychotic effects by enhancement of glutamatergic functions as well as by the blockade of dopamine receptors.
A hydrophobic, fibrillogenic peptide fragment of human prion protein (PrP106-126) had in vitro toxicity to neurons expressing cellular prion protein (PrP(C)). In this study, we proved that primary cultures of mouse cerebral endothelial cells (MCEC) express PrP(C). Incubation of MCEC with PrP106-126 (25-200 microM) caused a dose-dependent toxicity assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase release, bis-benzimide staining for nuclear morphology, and trypan blue exclusion test. Pentosan polysulphate (50-100 microg/ml), a drug effective in scrapie prophylaxis, dose-dependently attenuated the injury. MCEC cultures from mice homogenous for the disrupted PrP gene were resistant to the toxicity of PrP106-126. In conclusion, cerebral endothelium expressing PrP(C) may be directly damaged during spongiform encephalopathies.