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ABSTRACT: Adenosine deaminase in the hypothalamic tuberomammillary nucleus and median eminence of rat and mouse brains was investigated with two different antibodies generated against the enzyme derived from either calf or mouse. Both antibodies labelled neurons in the tuberomammillary nucleus and, as determined in rat, they immunolabelled the same neurons. In the median eminence, immunopositive fibres and terminals were detected with anti-mouse adenosine deaminase in both rat and mouse, while no such staining was seen in either species with antibody against the calf enzyme. These fibres were most concentrated in the external median eminence, had a more restricted distribution than those containing either galanin or tyrosine hydroxylase and only partially overlapped with oxytocin-positive fibres. By electron microscopy, adenosine deaminase was found in terminals containing both small, clear vesicles with diameters of 35 to 45 nm and large dense-core vesicles with diameters of 100 to 140 nm. Preadsorption of antibodies with purified enzyme derived from the species against which they were directed eliminated all staining in rat, while antibody adsorptions across species were less effective. Preadsorption of anti-mouse adenosine deaminase antibody with the mouse deaminase led to increased labelling in mouse median eminence, suggesting an interaction between tissue components and antibody-linked enzyme. Tests for the presence of adenosine deaminase-complexing protein (CD26) with an antibody against this protein gave positive labelling in the median eminence of both species and this labelling was co-distributed with that seen for adenosine deaminase. These results confirm the expression of adenosine deaminase in restricted populations of neurons in rodent brain as revealed with a novel antibody, suggest the presence of a distinct form or localization of the enzyme in the median eminence, and raise the possibility that it contributes, perhaps along with CD26, to purinergic regulation of hormone secretion in this structure.
Neuroscience 08/1996; 73(2):459-71. · 3.38 Impact Factor
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ABSTRACT: C-terminals can be distinguished at the ultrastructural level from other types of nerve endings on motoneurons by their prominent and regularly occurring postsynaptic specializations termed subsurface cisterns (SSC). We have previously shown (Yamamoto et al., 1991) that an antibody directed against a sequence within the gap junction protein connexin32 immunolabels these motoneuronal SSCs and can therefore serve as a immunohistochemical tool to visualize indirectly the location of C-terminals on motoneurons at the light microscope level. Here we have used this anti-SSC antibody in combination with antibodies against choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) to determine whether C-terminals on motoneurons contain these cholinergic enzyme markers. In sections at all major spinal cord levels and in several cranial motor nuclei examined, motoneuronal cell bodies and their proximal dendrites were studded with large ChAT-immunoreactive (ChAT-IR) boutons. Boutons having a similar distribution and appearance on motoneurons were also immunolabeled for AChE. In addition, motoneurons were surrounded by a dense plexus of AChE-immunoreactive (AChE-IR) varicose fibers and fine preterminal axons. In double-labeled sections, AChE-IR boutons corresponded to those immunolabeled for ChAT. In sections processed for simultaneous immunofluorescence detection of ChAT and SSCs, ChAT-IR boutons were very often found in apposition to immunolabeled SSCs. In sections processed for simultaneous labeling of AChE and SSCs. AChE-IR boutons were again frequently seen abutting labeled SSCs. These results provide the first strong evidence at the LM level that a large proportion, if not the entirety, of C-terminals are cholinergic and show that these terminals consist in part of relatively large varicosities along highly varicose axons that form en passant type contacts on motoneurons. At the same time, our results substantially narrow possibilities regarding the as yet undetermined source of C-terminals, which can now be considered to originate from cholinergic neurons, such as those located in the brainstem and/or the spinal cord.
Synapse 10/1993; 15(1):17-32. · 2.94 Impact Factor
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ABSTRACT: Immunohistochemical methods were employed to investigate the cellular and ultrastructural localization of the gap junction protein connexin43 (Cx43) in rat pituitary. Western blots of pituitary homogenates probed with anti-Cx43 antibodies showed the presence of Cx43 in both anterior and posterior pituitary lobes. By light microscopy (LM), Cx43-immunoreactive (Cx43-IR) puncta were found in all areas of the posterior lobe, but at greater concentrations in peripheral regions of this structure. By electron microscopy (EM), immunogold labelling for Cx43 was seen at gap junctions between thin cytoplasmic processes of pituicytes. No immunoreactivity was detected in the intermediate lobe. The anterior lobe contained puncta similar to but more sparsely scattered than those in the posterior lobe, and by EM analysis these were demonstrated to correspond to labelled gap junctions between stellate cells. In addition, anti-Cx43 antibodies produced intracellular labelling in a small percentage of endocrine cells, which were distributed throughout the anterior lobe and determined by double immunostaining methods to be cells containing luteinizing hormone. By EM, labelling within these cells was associated with predominantly large secretory granules and other loosely organized organelles. The results indicate that gap junctions in the pituitary are composed of Cx43 and that this or a related protein may have a novel intracellular function within gonadotrophs.
Histochemistry 08/1993; 100(1):53-64.
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ABSTRACT: We have shown previously that connexin43 in the adult rat central nervous system (CNS) is predominantly localized at astrocytic gap junctions. Here we document immunohistochemically the emergence of connexin43-immunoreactive (connexin43-IR) structures and the regional patterns of connexin43 expression during postnatal maturation of the rat brain. On Western blots, connexin43 was detected in brain samples at postnatal day (P) 5, the earliest age studied. Immunohistochemically, most brain regions displayed a characteristic sequence of transient immunoreactive profiles that ultimately gave rise to the uneven distribution of the protein seen in adults. Generally, brains at P1-P5 exhibited long, fibrous connexin43-IR elements which were identified as radial glial cells. This fibrous immunostaining was considerably diminished at P5 and was replaced by short immunoreactive processes which predominated up to P10. These processes had a stellate appearance, emanated from partially stained astrocytic cell bodies and were heterogeneously distributed throughout the developing brain. By P15, there occurred only punctate immunolabelling similar to that seen in adult brain. Some brain regions including the amygdaloid complex, septohypothalamic nucleus, preoptic hypothalamus, zona incerta, ependyma and subfornical organ were exceptional in that they displayed adult immunostaining patterns at early postnatal ages suggesting a precocious maturation of gap junctions in these areas. We conclude that the highly heterogeneous distribution of connexin43-immunoreactivity among defined nuclear structures in adult brain does not reflect an antecedent requirement for connexin43 in early brain morphogenesis, but rather is related to the development of neuronal activity, the establishment of functional circuitry and the contribution of astrocytic gap junctions to glial metabolic coupling and potassium spatial buffering in the mature CNS.
Developmental Brain Research 05/1992; 66(2):165-80. · 1.78 Impact Factor
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ABSTRACT: We used Western blot and immunohistochemical methods to investigate the biochemical characteristics and cellular distribution of a novel peptide (peptide 23) that was previously shown to be released from anterior pituitary cells of rat in response to growth hormone-releasing hormone. In the pituitary, peptide 23 isolated from intact cells had an Mr of 31,000, whereas that released into culture medium had an Mr of 16,000. Pancreatic islets contained a 19 KD form of the peptide. Immunohistochemically, peptide 23 in the rat pituitary gland was localized in a subpopulation of somatotropes. In pancreatic islets, the peptide was found by triple immunofluorescence labeling to be present in both insulin- and somatostatin-containing cells. In the gastrointestinal tract, peptide 23 was found only in a subpopulation of endocrine cells in the pyloric glands. This subpopulation of cells was found to be entirely separate from those containing either serotonin or somatostatin, and may represent one of the other known or as yet biochemically uncharacterized cell types in this gland. The results suggest that in response to secretagogues in vitro, an altered form of the peptide is secreted from pituitary cells and that an intracellular form of peptide 23 is expressed in some but not all somatotropes, a large proportion of islet cells, and a distinct population of pyloric cells.
Journal of Histochemistry and Cytochemistry 03/1992; 40(2):221-9. · 2.72 Impact Factor
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ABSTRACT: We have shown by immunohistochemical methods that the gap junction protein connexin43 is heterogeneously distributed in rat brain (Yamamoto et al: J Comp Neurol 302:853, 1990). Here we have compared quantitatively the relative amount of connexin43 detected on Western blots of seven central nervous system (CNS) regions with the density of connexin43-immunoperoxidase reactivity in these regions. As has been observed on Western blots of several cell types, homogenates of these CNS regions contained two forms of connexin43, its dephospho form with an apparent mobility of approximately 41 kDa and its approximately 43 kDa phosphorylated form. While the relative quantities of connexin43 varied considerably among the brain regions, the ratio of the 43/41 kDa forms, 0.71, was relatively uniform (correlation coefficient, r = 0.92). Sections of brain processed for connexin43-immunolocalization by the peroxidase-antiperoxidase (PAP) method showed that chromogen deposition was linear with incubation time in reaction medium. Optical density of tissue connexin43-immunoreactivity in each of the seven areas plotted against the density of connexin43 bands on Western blots gave a correlation coefficient of r = 0.90. Connexin43-immunoreactivity had a similar appearance in sections processed by PAP or immunofluorescence procedures and consisted of isolated or aggregates of puncta.(ABSTRACT TRUNCATED AT 250 WORDS)
Glia 02/1992; 5(1):1-9. · 4.82 Impact Factor
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ABSTRACT: Basic fibroblast growth factor (bFGF) is a ubiquitous and multifunctional polypeptide that is believed to have a role in tissue repair and to act as a morphogen in embryonic development. Here, we have used immunohistochemical and biochemical methods with antibodies directed against the amino-terminal domain of bFGF, designated IS2, which recognize native and denatured bFGF, to demonstrate that in addition to its known intracellular and extracellular localization in heart, bFGF is also associated with cardiomyocyte gap junctions. In tissue sections, IS2 labeled regions of intercalated discs, producing an immunofluorescence pattern virtually indistinguishable from that obtained with antibodies against the heart gap junction protein connexin-43. By electron microscopy, gap junctions but not other regions of plasma membrane were heavily immunolabeled with this antibody. By solid phase immunoassay, bFGF was found to be more concentrated in a fraction enriched in cardiac gap junctions than in whole sarcolemmal preparations. Finally, an 18-kDa protein was recognized by several different antibodies specific for bFGF on Western blots of heart subcellular fractions enriched in gap junctions. We suggest that bFGF-like peptides are either an integral part of, or exist in close association with, cardiac gap junctions and thus may play a role in modulating gap junctional intercellular communication.
Journal of Biological Chemistry 11/1991; 266(29):19551-7. · 4.77 Impact Factor
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ABSTRACT: Recent studies have established that the gap junction protein connexin43 is a major structural component of gap junctions between astrocytes in rat brain. Here, we investigated by immunohistochemical methods the effect of kainic acid-induced neuronal degeneration on connexin43 expression by astrocytes. Stereotaxic injections of kainic acid into the thalamus were found to cause a near total depletion of connexin43-immunoreactivity at the lesion site. Areas depleted of connexin43 corresponded to those exhibiting substantial neuronal loss and intense gliosis. These results implicate a neuronal contribution to the regulation of connexin43 expression by astrocytes and, hence, to local control of the potassium spatial buffering capacity afforded by astrocyte gap junctions.
Neuroscience Letters 10/1991; 130(1):120-4. · 2.11 Impact Factor
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ABSTRACT: Light and electron microscope procedures and antibodies against basic fibroblast growth factor (bFGF) were used to study the immunohistochemical localization of bFGF in rat brain. Throughout all areas of the brain analyzed by LM including grey matter, white matter, ependyma, and leptomeninges bFGF-immunoreactivity consisted of punctate immunolabelling that had an appearance and heterogenous distribution nearly identical to that displayed by the gap junction protein connexin43. By immuno-EM, bFGF was localized to gap junctions between astrocytes. It appears that there is a physical association of bFGF with gap junctions composed of connexin43 and it is suggested that bFGF may exert a regulatory influence on intercellular communication at such junctions.
Brain Research 08/1991; 554(1-2):336-43. · 2.73 Impact Factor
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ABSTRACT: A monoclonal antibody against amino acids 224-234 of the gap junction protein connexin32 was found by immunohistochemistry to label subsurface cisterns (SSCs) in alpha-motoneurons of the rat (Yamamoto et al., 1990) and was used here to document by light (LM) and electron microscopy (EM) the appearance of immunoreactive SSCs in motoneurons of the rat and cat. This antibody and a polyclonal antibody against connexin32 labelled gap junctions in rat liver as well as SSCs in facial motoneurons. By LM, SSCs were seen as labelled puncta on motoneuronal perikarya and proximal dendrites. In the rat, they appeared to be present on all motoneurons at cranial and spinal levels, but varied considerably in size and number among motor nuclei. Labelled SSCs were the smallest and most sparse in motoneurons of the dorsal vagal motor nucleus, moderate in size and most numerous in the trochlear, oculomotor, and trigeminal motor nuclei, and largest though less densely distributed in spinal motoneurons. Dendrites were seen to contain SSCs for distances of up to 230 micron from their somal origin. Labelling within individual SSCs seen en face consisted of either numerous small puncta or linear arrays of immunoreactivity. By EM, labelled SSCs in the rat facial nucleus were always seen beneath a cluster of C-terminals. Immunolabelling was most dense in the space between the plasma membrane and SSC, which we define as the subsurface cisternal cleft. The SSCs were usually intermittently labelled along their length and exhibited a narrow luminal space ranging from 2 to 5 nm. On the basis of structural analogies between SSCs in neurons and the sacroplasmic reticulum terminal cistern/T-tubule complex in muscle, SSCs have previously been suggested to be important sites of calcium mobilization. The constant association of C-terminal with SSCs in motoneurons may represent a useful model in which to study SSC function as well as to investigate the possible presence of a connexinlike protein at regions of SSCs that form a narrow lumen similar to that at gap junctions.
Synapse 07/1991; 8(2):119-36. · 2.94 Impact Factor
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ABSTRACT: Light and electron microscopic immunohistochemical techniques were used to investigate the central projections and colocalization relationships of a subpopulation of primary afferent neurons that were immunolabelled with an antibody (AB893) against rat liver gap junctions. In lumbar dorsal root ganglia AB893-immunoreactivity was seen in 14.5% of all cells and in both small and large size neurons. Colocalization analysis showed that 78% of all AB893-immunoreactive (AB893-IR) neurons contained calcitonin gene-related peptide, while only 7 to 10% contained the calcium binding proteins parvalbumin or calbindin D28k. Among small type B AB893-IR ganglion cells, it was calculated that over 90% contained fluoride-resistant acid phosphatase, while only 1 to 2% contained substance P or somatostatin. Cytochrome oxidase histochemistry revealed light staining in the vast majority of AB893-IR cells. In the dorsal horn of the spinal cord the antibody labelled fibers in the dorsal root, Lissauer's tract, lamina I and lamina II. Isolated immunoreactive fiber bundles were arranged in sheets spanning most of lamina II. Immunoreactive fibers were depleted from the dorsal horn after dorsal rhizotomy or neonatal capsaicin treatment. Ultrastructural examination showed that AB893-IR fibers were composed of closely associated clusters of 2 to 5 unmyelinated fibers each ranging from 0.1-0.4 microns in diameter. Immunoreactivity was distributed intermittently along the cytoplasmic membrane of axons and en passant sinusoid terminals located centrally within the fiber clusters, as well as along axonal membranes adjacent to the central axon or terminal. The results suggest that the immunoreactive fibers in lamina II of the dorsal horn originate from a subpopulation of AB893-IR neurons that contain FRAP and give rise to unmyelinated axons.
Brain Research Bulletin 07/1991; 26(6):825-43. · 2.82 Impact Factor
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ABSTRACT: Histochemical detection of cytochrome oxidase activity has been widely used to deduce patterns of neuronal electrical activity in the CNS. Here we investigated the utility of cytochrome oxidase localization by immunohistochemistry and compared immunostaining with histochemical staining patterns in dorsal root ganglia of the rat. In addition, a limited survey of cytochrome oxidase immunostaining density within what are thought to be highly active parvalbumin-immunoreactive neurons was conducted. The immunohistochemical approach produced granular cytoplasmic immunolabelling in neuronal cell bodies and allowed identification of individual labelled cells in all brain regions including those within dense immunoreactive networks of neuropil. Neuronal somata exhibited a wide range of staining densities which were particularly evident in the hippocampus and dorsal root ganglia. The distribution of neurons intensely immunoreactive for cytochrome oxidase within various structures was consistent with previous histochemical descriptions of enzyme activity. Densitometric measurements of immunohistochemical reaction product in individual neurons of hippocampus, substantia nigra, cerebellum and dorsal root ganglia showed that the rate of product deposition was linear with time under conditions chosen for comparisons of staining density. Quantitative analysis of cytochrome oxidase immunohistochemical and histochemical staining densities within the same cells in adjacent sections of dorsal root ganglion gave a correlation coefficient of r = 0.75 (P less than 0.001). In sections processed immunohistochemically for both cytochrome oxidase and parvalbumin, most but not all parvalbumin-containing cells displayed dense cytochrome oxidase immunolabelling. Conversely, many examples were found of neurons that were densely stained for cytochrome oxidase, but lacked parvalbumin. Immunohistochemistry for cytochrome oxidase reveals the enzyme in neuronal cell bodies with a clarity not usually seen with the histochemical method. Combination of this immunohistochemical approach with simultaneous immunolabelling of other neuronal markers, as shown here in the case of parvalbumin, is expected to assist the elucidation of patterns of activity in neurochemically identified cell types and anatomically defined neural systems.
Neuroscience 02/1991; 40(3):825-39. · 3.38 Impact Factor
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ABSTRACT: Gap junctions and the intercellular communication syncytium they form between glial cells are thought to play a critical role in glial maintenance of appropriate metabolic environments in neural tissues. We have previously suggested (Yamamoto et al., Brain Res. 508:313-319, '90) that the vast majority of astrocytes in rat brain express connexin43, one of several recently identified gap junction proteins. Here, we confirm ultrastructurally that astrocytes in a number of brain regions of rat are immunolabelled with an antibody against connexin43 and that neurons and oligodendrocytes are devoid of labelling. The distribution of connexin43 immunoreactivity throughout the brain is presented at the light microscope (LM) level. By LM, immunoreactive structures consisted primarily of round or elongated puncta ranging from 0.3 microns to 4 microns in length and of annular profiles ranging from 1 to 10 microns in diameter. Immunolabelled fibrous processes were only occasionally seen and no labelling was observed in astrocytic cell bodies. Long, linear arrays of puncta were rare in gray matter but were common in white matter where they were arranged parallel to myelinated fibers. Puncta organized in a honeycomb pattern were seen near the cerebral cortical surface and frequently around blood vessels. Regional immunoreaction density, which was a reflection of either the concentration or staining intensity of immunoreactive elements, was remarkably heterogeneous; dramatic differences in labelling intensity frequently delineated anatomical boundaries between adjacent nuclei. Abrupt as well as graded fluctuations of immunoreaction intensity were also observed within nuclear structures. By electron microscopy (EM), gap junctions of fibrous and protoplasmic astrocytes were intensely stained and labelled organelles were often observed intracellularly in areas near gap junctions. These junctions and the spread of immunoreaction product to perijunctional organelles in their vicinity were considered to correspond to puncta seen by LM. Labelling within astrocytic cell bodies was seen in only a few instances. In some brain areas, astrocytic processes commonly gave rise to immunoreactive lamellae that partially ensheathed neuronal cell bodies, axon terminals, dendrites, and synaptic glomeruli. Such lamellae were considered to correspond to immunoreactive annular profiles seen by LM. Perivascular endfoot processes of astrocytes displayed intense staining of their gap junctions and portions of their apposing membranes.(ABSTRACT TRUNCATED AT 400 WORDS)
The Journal of Comparative Neurology 01/1991; 302(4):853-83. · 3.81 Impact Factor
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ABSTRACT: Neurons in the tuberomammillary nucleus (TM) of the rat hypothalamus were immunolabelled for the enzyme adenosine deaminase (ADA) and investigated by electron microscopic immunohistochemical techniques. ADA-immunoreactivity was distributed throughout the somal and dendritic cytoplasm of TM neurons and in the karyoplasm of most, but not all of these neurons. Immunoreactive axons were rarely observed within the tightly packed cell clusters of the TM subdivisions examined. Dense deposition of immunoreaction product together with reasonable preservation of morphological detail facilitated identification of immunoreaction product together with reasonable preservation of morphological detail facilitated identification of immunoreactive profiles and allowed characterization of the ultrastructural features of labelled neurons and the relationships of these with each other and with surrounding unlabelled neuronal and glial elements. Immunolocalization of ADA therefore represents a reliable and convenient method for the identification of TM neurons in EM studies of their ultrastructure and synaptic interactions.
Brain Research 10/1990; 527(2):335-41. · 2.73 Impact Factor
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ABSTRACT: Several lines of evidence indicate the existence of channels that mediate the movement of calcium from the extracellular space directly into some intracellular calcium storage compartment and from one intracellular membrane-bounded compartment to another. The possibility that such channels resemble intercellular communication pathways formed by gap junction proteins (connexins) was investigated in rat brain. Antibodies against a rat liver gap junction protein (connexin32) were found to recognize several distinct proteins on Western blots of brain homogenates. In motoneurons these antibodies immunohistochemically labelled portions of neuronal endoplasmic reticulum membranes that form subsurface cisterns (SSCs) adjacent to the plasma membrane. These results suggest that SSCs and connexin-like proteins may be involved in the process of calcium mobilization in neurons.
Brain Research 10/1990; 527(1):135-9. · 2.73 Impact Factor
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ABSTRACT: A site-specific antibody against the principal gap junctional protein in heart (connexin 43) was used to determine immunohistochemically the cellular localization of this protein in rat brain. Structures labelled with the antibody included gap junctional membranes between glial, ependymal, pial and arachnoid cells as well as cytoplasmic membranes and intracellular organelles in close proximity to junctions between these various cell types. No labelling was detected within cell bodies of oligodendrocytes and neurons and no labelled neuronal gap junctions were found. The results suggest that connexin 43 is one of the major gap junctional proteins utilized for junctional coupling between astrocytes and between cells lining the surfaces of the brain.
Brain Research 03/1990; 508(2):313-9. · 2.73 Impact Factor
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ABSTRACT: Immunohistochemical and histochemical techniques were used to re-examine the extent to which neonatal capsaicin treatment depletes calcitonin gene-related peptide in the dorsal horn of the spinal cord, to determine the localization of calcitonin gene-related peptide in relation to that of fluoride-resistant acid phosphatase in lumbar dorsal root ganglia, and to compare the distribution of these primary afferent markers in the dorsal horn. A substantial depletion of calcitonin gene-related peptide was observed in the dorsal horn of adult rats treated neonatally with capsaicin suggesting that a large proportion of this peptide in the dorsal horn is contained within capsaicin-sensitive primary afferent fibers. In dorsal root ganglia 30% of all or 44% of small- and medium-sized calcitonin gene-related peptide-immunoreactive cells were positive for fluoride-resistant acid phosphatase. Conversely, 50% of cells positive for the phosphatase enzyme also displayed immunoreactivity for the peptide. In lamina II of the dorsal horn calcitonin gene-related peptide and fluoride-resistant acid phosphatase were found to have an overlapping distribution. The presence of fluoride-resistant acid phosphatase in a substantial proportion of neuropeptide-containing primary sensory neurons suggests a lack of segregation of sensory neuronal populations into peptide- and non-peptide-containing subgroups at least on the basis of non-peptide neurons defined as those containing fluoride-resistant acid phosphatase.
Neuroscience 02/1990; 36(3):751-60. · 3.38 Impact Factor
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ABSTRACT: Immunohistochemical techniques were utilized to investigate the distribution and morphology of neurons containing the calcium binding proteins parvalbumin (PV) and calbindin D28k (CaBP) in the superficial layers of rat spinal cord. Most PV-immunoreactive (PV-IR) neurons were restricted to a 25 to 60 microns thick band straddling the border between lamina II and III. Positive somata had long rostrocaudally oriented dendrites confined to narrow sagittally arranged sheets within this band and axons that entered lamina II or the superficial portions of lamina III. Long varicose axons, presumed to originate from these cells, were moderately distributed in Lissauer's tract and lamina II. CaBP-immunoreactive (CaBP-IR) neurons were found within lamina I and throughout lamina II. Large calibre PV-IR and CaBP-IR axons were seen in the dorsal column and the lateral funiculus. Dorsal rhizotomy or neonatal capsaicin treatment appeared to have no effect on PV-IR and CaBP-IR elements in the superficial lumbar dorsal horn. However, dorsal rhizotomy reduced the number of positive axons in the dorsal column and in deeper lamina of the dorsal horn. These results add to the known lamination patterns of the superficial dorsal horn and point to the existence of a lamina defined by PV-positive neurons at the lamina II/III border. These neurons may have electrophysiological characteristics attributed to PV- or CaBP-containing neurons elsewhere in the CNS.
Brain Research Bulletin 01/1990; 23(6):493-508. · 2.82 Impact Factor
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ABSTRACT: Electrotonic transmission via gap junctions appears to be essential for both the relay and integration of information in nuclear groups involved in the electrolocation and electrocommunication systems of weakly electric fish. An affinity-purified antibody against the 27 kD gap-junctional polypeptide (GJP) from rat liver was used to determine immunohistochemically the distribution of GJP-immunoreactivity (GJP-IR) in electrosensory structures and some other brain regions of the gymnotiform fish, Apteronotus leptorhynchus. At the ultrastructural level, immunolabelling with this antibody was localized, in part, to neuronal and glial gap junctions where it was assumed to recognize a junctional polypeptide. By light microscopy, the vast majority of immunoreactive elements appeared either as fine puncta or as varicosities along fibers that exhibited immunostained intervaricose segments. Diffuse immunoreactivity within cell bodies was rare, being most evident in giant relay neurons and presumptive glial cells within the pacemaker nucleus and in neurons within the posterior raphe nucleus. The distribution of punctate and fibrous GJP-IR was remarkably heterogeneous with respect to density; large areas of the forebrain and most major fiber tracts were nearly devoid of immunoreactivity, whereas concentrations of puncta delineating patches within the inferior lobe of the hypothalamus and the vagal sensory nucleus were so dense as to appear as uniform deposition of immunoperoxidase reaction product at low magnification. Some structures known to be associated with the electrosensory system, including the nucleus electrosensorius and nucleus praeeminentialis, were among the brain regions containing the highest concentrations of immunoreactivity. At the cellular level, expected patterns of GJP-IR were observed in the pacemaker nucleus, torus semicircularis, and electrosensory lateral line lobe. In each of these structures punctate immunoreactivity was seen in apposition to cell bodies or dendrites of neurons known to receive gap junction contacts. In addition, the dendrites of neurons within the prepacemaker nucleus were laden with a striking array of puncta, suggesting that interactions via gap junctions may be a significant feature of these neurons. These immunohistochemical results are consistent with previous electrophysiological and ultrastructural observations pointing to the importance of electrotonic communication in the electrosensory system of weakly electric fish, and suggest that gap junctions may also contribute to neural transmission in central nervous system related to other functions in these teleosts.(ABSTRACT TRUNCATED AT 400 WORDS)
The Journal of Comparative Neurology 12/1989; 289(3):509-36. · 3.81 Impact Factor
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ABSTRACT: Sections of lumbar dorsal root ganglia from rat were analyzed by immunohistochemical techniques to determine the size distribution and numbers of cells containing parvalbumin and calbindin D28k and to establish their coexistence relationships with each other and with cells containing calcitonin gene-related peptide (CGRP). The proportion of ganglia cells containing parvalbumin and calbindin D28k was 14% and 22%, respectively. The majority of cells immunoreactive for these proteins were of the large A type. Parvalbumin was colocalized almost completely (greater than 99%) with with calbindin D28k and minimally (less than 1%) with CGRP. Only 9% of the calbindin D28k-positive cells were immunoreactive for CGRP.
Brain Research 10/1989; 497(1):163-70. · 2.73 Impact Factor
