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PubMed2002

Calcium-binding proteins map the postnatal development of rat vestibular nuclei and their vestibular and cerebellar projections.

We investigated whether three calcium-binding proteins, calretinin, parvalbumin, and calbindin, could identify specific aspects of the postnatal development of the rat lateral (LVN) and medial (MVN) vestibular nuclei and their vestibular and cerebellar connections. Calretinin levels in the vestibular nuclei, increased significantly between birth and postnatal day (P) 45. In situ hybridization and immunocytochemical staining showed that calretinin-immunoreactive neurons were mostly located in the parvocellular MVN at birth and that somatic and dendritic growth occurred between birth and P14. During the first week, parvalbumin-immunoreactive fibers and endings were confined to specific areas, i.e., the ventral LVN and magnocellular MVN, and identified exclusively the maturation of the vestibular afferents. Calbindin was located within the dorsal LVN and the parvocellular MVN and identified the first arrival of the corticocerebellar afferents. From the second week, in addition to labeling vestibular afferents in their specific target areas, parvalbumin was also found colocalized with calbindin in mature Purkinje cell afferents. Thus, the specific spatiotemporal distribution of parvalbumin and calbindin could correspond to two successive phases of synaptic remodeling involving integration of the vestibular sensory messages and their cerebellar control. On the basis of the sequence of distribution patterns of these proteins during the development of the vestibular nuclei, calretinin is an effective marker for neuronal development of the parvocellular MVN, parvalbumin is a specific marker identifying maturation of the vestibular afferents and endings, and calbindin is a marker of the first appearance and development of Purkinje cell afferents.

Animals↗
PubMed2002

Retinoic acid signaling at sites of plasticity in the mature central nervous system.

We used transgenic reporter mice to determine whether brain regions that respond to retinoic acid (RA) during development do so in maturity. We focused on two prominent sites of embryonic RA signaling: the dorsal spinal cord and the olfactory bulb. In the mature dorsal spinal cord, expression of a direct repeat 5 RA response element (DR5-RARE) transgene is seen in interneurons in laminae I and II, as well as in ependymal cells around the central canal. In the olfactory bulb, DR5-RARE transgene-expressing neurons are seen in the mature granule cell and periglomerular layers, as well as in cells in the subventricular zone of the forebrain-the established source for newly generated granule and periglomerular neurons. In addition, there are transgene-labeled neurons in a small number of other brain regions. These include the spinal trigeminal nucleus, area postrema, habenula, amygdala, and the cerebral cortex. Thus, a distinct type of RA-mediated gene expression, detected with the DR5-RARE reporter transgene, defines neurons, subependymal, or ependymal cells in discrete locations throughout the neuraxis. Some of these cells--particularly those in the spinal cord and olfactory bulb--are found in central nervous system regions that receive local RA signals early in development, and retain a significant amount of functional or structural plasticity in the adult.

Aldehyde Oxidoreductases↗
PubMed2002

Chemoarchitecture of GABAergic neurons in the ferret superior colliculus.

gamma-Aminobutyric acid (GABA)ergic neurons are thought to play a key role both in visual processing and in the complex sensory-motor transformations that take place in the mammalian superior colliculus. To understand the organization of GABAergic neurons in the ferret superior colliculus, we applied antisera to several markers of GABAergic function, including GABA, two isoforms of its synthetic enzyme glutamic acid decarboxylase (GAD-65 and GAD-67), and the GABA transporter, GAT-1. We also applied antisera to several calcium binding proteins (calbindin [CB], calretinin [CR], and parvalbumin [PV]) and neuronal nitric oxide synthase (NOS), chemical markers that colocalize with GABA in some areas of the central nervous system. The distribution of GABAergic neurons in the ferret is similar to that of other mammalian species. GABAergic neurons in the ferret superior colliculus were small, morphologically diverse, and widely distributed throughout all layers of the colliculus. As has been shown in other mammalian species, neurons expressing PV, CB, CR, and NOS were differentially distributed in layers and patches throughout the ferret colliculus. None of these markers, however, showed a distribution that mirrored that of GABAergic neurons. Furthermore, few GABAergic neurons colocalized these neurochemical markers. Only 14% of GABAergic neurons in the superficial layers and 18% of neurons in the deeper layers colocalized PV, 14% of GABAergic neurons in the superficial layers and 10% in the deeper layers colocalized CB, and only 1% of GABAergic neurons in both the superficial and deep layers colocalized nitric oxide synthase. Thus, the arrangement of GABAergic neurons in the ferret superior colliculus is broadly distributed and is distinct from other recognized organizational patterns in the superior colliculus.

Animals↗
PubMed2003

Parvalbumin, calbindin, or calretinin in cortically projecting and GABAergic, cholinergic, or glutamatergic basal forebrain neurons of the rat.

The basal forebrain (BF) plays an important role in modulating cortical activity and facilitating processes of attention, learning, and memory. This role is subserved by cholinergic neurons but also requires the participation of other noncholinergic neurons. Noncholinergic neurons include gamma-amino butyric acidergic (GABAergic) neurons, some of which project in parallel with the cholinergic cells to the cerebral cortex, others of which project caudally or locally. With the original aim of distinguishing different subgroups of GABAergic neurons, we examined immunostaining for the calcium binding proteins (CBPs) parvalbumin (Parv), calbindin (Calb), and calretinin (Calret) in the rat. Although the CBP(+) cell groups were distributed in a coextensive manner with the GABAergic cells, they were collectively more numerous. Of cells retrogradely labeled with cholera toxin (CT) from the prefrontal or parietal cortex, Parv(+) and Calb(+) cells, but not Calret(+) cells, represented substantial proportions ( approximately 35-45% each) that collectively were greater than that of GABAergic projection neurons. From dual immunostaining for the CBPs and glutamic acid decarboxylase (GAD), it appeared that the vast majority (>90%) of the Parv(+) group was GAD(+), whereas only a small minority (<10%) of the Calb(+) or Calret(+) group was GAD(+). Significant proportions of Calb(+) (>40%) and Calret(+) (>80%) neurons were immunopositive for phosphate-activated glutaminase, the synthetic enzyme for transmitter glutamate. The results suggested that, whereas Calret(+) cells predominantly comprise caudally or locally projecting, possibly glutamatergic BF neurons, Parv(+) cells likely comprise the cortically projecting GABAergic BF neurons and Calb(+) cells the cortically projecting, possibly glutamatergic BF neurons that would collectively participate with the cholinergic cells in the modulation of cortical activity.

Acetylcholine↗
PubMed2003

Cortical and brainstem neurons containing calcium-binding proteins in a murine model of Duchenne's muscular dystrophy: selective changes in the sensorimotor cortex.

In the muscular dystrophic (mdx) mouse, which is characterized by deficient dystrophin expression and provides a model of Duchenne's muscular dystrophy, we previously demonstrated marked central nervous system alterations and in particular a quantitative reduction of corticospinal and rubrospinal neurons and pathologic changes of these cells. Prompted by these findings and in view of the relations between calcium ions and dystrophin, we analyzed with immunohistochemistry the neurons containing the calcium-binding proteins parvalbumin, calbindin D28k, and calretinin in cortical areas and brainstem nuclei of mdx mice. In the sensorimotor cortex, parvalbumin-positive and calbindin-positive neurons, which represent a subset of cortical interneurons, were significantly more numerous in mdx mice than in wild-type ones. In addition, the laminar distribution of parvalbumin-positive neurons in the motor and somatosensory cortical areas of mdx mice was altered with respect to wild-type animals. No alterations in the number and distribution were found in the parvalbumin- or calbindin-expressing cell populations of the visual and anterior cingulate cortices of mdx mice. The pattern of calretinin immunoreactivity was normal in all investigated cortical areas. The cell populations containing either calcium-binding protein were similar in brainstem nuclei of mdx and wild-type mice. The present findings demonstrated selective changes of subsets of interneurons in the motor and somatosensory cortical areas of mdx mice. Therefore, the data showed that, in the cortices of these mutant animals, the previously demonstrated pathologic changes of corticospinal cell populations are accompanied by marked alterations in the local circuitry.

Animals↗
PubMed2003

Characterization of the human superior olivary complex by calcium binding proteins and neurofilament H (SMI-32).

This study provides a morphologic characterization of the human superior olivary complex as revealed by immunohistochemistry by using antibodies against the calcium binding proteins parvalbumin, calbindin, calretinin, and the nonphosphorylated neurofilament H SMI-32. By combining these markers, it was possible to establish the neuronal architecture and details of the morphologic organization (including axonal terminals) of the different nuclei. The medial superior olivary nucleus is formed by a sheet of parallel-oriented cells. A clear segregation of axon terminals was noticed on the medially and laterally oriented dendrites of the mostly bipolar neurons. The lateral superior olivary nucleus lacked a distinct nuclear shape but was formed by several patches of rather irregularly arranged neurons. Calretinin or parvalbumin immunoreactive afferent terminals were observed which contacted somata or dendrites of these neurons. The immunolabeling also revealed the boundaries of the dorsal periolivary nucleus and morphologic detail of its neurons. A coherent nuclear structure that could be addressed as the medial nucleus of the trapezoid body was not identified by any single one or by combinations of the markers used. The data were also used to establish a three-dimensional-reconstruction of the three major subnuclei of the superior olivary complex. The results are discussed with respect to the possible role of the superior olivary complex in the processing of spatial acoustic information in the azimuthal plane.

Calbindin 2↗
PubMed2003

Glutamate receptor subunit 3 (GluR3) immunoreactivity delineates a subpopulation of parvalbumin-containing interneurons in the rat hippocampus.

Rasmussen's encephalitis is a childhood disease resulting in intractable seizures associated with hippocampal and neocortical inflammation. An autoantibody against the GluR3 subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors is implicated in the pathophysiology of Rasmussen's encephalitis. AMPA receptors mediate excitatory neurotransmission in the brain and contain combinations of four subunits (GluR1-4). Although the distributions of GluR1, GluR2, and GluR4 are known in some detail, the cellular distribution of GluR3 in the mammalian brain remains to be described. We developed and characterized a GluR3-specific monoclonal antibody and quantified the cellular distribution of GluR3 in CA1 of the rat hippocampus. GluR3 immunoreactivity was detected in all pyramidal neurons and astrocytes and in most interneurons. We quantified the intensity of GluR3 immunoreactivity in interneuron subtypes defined by their calcium-binding protein content. GluR3 immunofluorescence, but not GluR1 or GluR2 immunofluorescence, was significantly elevated in somata of parvalbumin-containing interneurons compared to pyramidal somata. Strikingly, increased GluR3 immunofluorescence was not observed in calbindin- and calretinin-containing interneurons. Furthermore, 24% of parvalbumin-containing interneurons could be distinguished from surrounding neurons based on their intense GluR3 immunoreactivity. This subpopulation had significantly elevated GluR3 immunoreactivity compared to the rest of parvalbumin-containing interneurons. Electron microscopy revealed enriched GluR3 immunoreactivity in parvalbumin-containing perikarya at cytoplasmic and postsynaptic sites. Parvalbumin-containing interneurons, potent inhibitors of cortical pyramidal neurons, are vulnerable in the brains of epileptic patients. Our findings suggest that the somata of these interneurons are enriched in GluR3, which may render them vulnerable to pathological states such as epilepsy and Rasmussen's encephalitis.

Animals↗
PubMed2003

Anatomical markers for the subdivisions of the barn owl's inferior-collicular complex and adjacent peri- and subventricular structures.

The anatomy of the inferior-collicular complex of the barn owl, situated below the fourth ventricle in the tectal lobe, was studied by determining the distribution of antigens with antibodies directed against tyrosine hydroxylase, gamma-aminobutyric acid (GABA)(Abeta), dopamine- and cyclic AMP-regulated phosphoprotein (DARPP-32), calretinin, and calbindin. Additionally, the somata were stained with cresyl violet, and fibers were marked according to the Gallyas procedure. These markers were chosen to allow for an easy delineation of the boundaries between the subnuclei of the inferior colliculus. We could discriminate eight structures that belong to the three subnuclei of the inferior colliculus [the central nucleus (ICC), the superficial nucleus (ICS), the external nucleus (ICX)] and to the optic tectum. Periventricular tectal layers 15a and 15b stained well with all the antibodies used. The ICS, embedded in tectal layer 15a, may be divided into a dorsal and a ventral lamina. It does not have direct contact with the other nuclei of the inferior colliculus. The border between tectal layer 15a and ICX was well marked by all antibodies, but less so in Gallyas and cresyl violet stains. The ICC consists of a core and a medial and lateral shell. The core was clearly demarcated with antibodies against calretinin and calbindin. The border between the lateral shell and the ICX was marked less well than the borders between ICX and 15a, but the somata were much more darkly labeled with the DARPP-32 antibody in ICX than in the lateral shell of ICC. None of the markers delineated the border between the medial and lateral shell of ICC.

Animals↗
PubMed2001

Chemical organization of the macaque monkey olfactory bulb: II. Calretinin, calbindin D-28k, parvalbumin, and neurocalcin immunoreactivity.

The distribution and morphologic features of calcium-binding protein- (calbindin D-28k, calretinin, neurocalcin, and parvalbumin) immunoreactive elements were studied in the macaque monkey olfactory bulb by using specific antibodies and the avidin-biotin-immunoperoxidase method. A characteristic laminar pattern of stained elements was observed for each marker. Scarce superficial short-axon cells and superficial stellate cells demonstrated calbindin D-28k immunoreactivity in the outer layers, whereas a moderate number of calbindin D-28k-immunoreactive granule cells and scarce deep short-axon cells were observed in the inner layers. Calretinin-staining demonstrated abundant periglomerular cells and granule cells and a scarce number of other interneuronal populations. Most neurocalcin-immunopositive elements were external and medial tufted cells and periglomerular cells, although other scarcer interneuronal populations were also immunostained. A few superficial and deep short-axon cells as well as small interneurons in the external plexiform layer were the only elements immunoreactive to parvalbumin. The distribution of the immunoreactive elements in the olfactory bulb of the macaque monkey showed a high similarity to that reported in the human, whereas it demonstrated a different and simpler pattern to what has been reported in the olfactory bulb of macrosmatic animals. It suggests more homogeneous calcium-mediated cell responses after stimulation that could be correlated to the lower capability to modulate olfactory signals in microsmatic animals. In addition, these results indicate that experimental models in rodents do not provide an accurate estimation of calcium-binding protein-immunoreactive neuronal populations in the primate olfactory system.

Animals↗
PubMed2001

A new subdivision of anterior piriform cortex and associated deep nucleus with novel features of interest for olfaction and epilepsy.

The anterior part of the piriform cortex (the APC) has been the focus of cortical-level studies of olfactory coding and associative processes and has attracted considerable attention as a result of a unique capacity to initiate generalized tonic-clonic seizures. Based on analysis of cytoarchitecture, connections, and immunocytochemical markers, a new subdivision of the APC and an associated deep nucleus are distinguished in the rat. As a result of its ventrorostral location in the APC, the new subdivision is termed the APC(VR). The deep nucleus is termed the pre-endopiriform nucleus (pEn) based on location and certain parallels to the endopiriform nucleus. The APC(VR) has unique features of interest for normal function: immunostaining suggests that it receives input from tufted cells in the olfactory bulb in addition to mitral cells, and it provides a heavy, rather selective projection from the piriform cortex to the ventrolateral orbital cortex (VLO), a prefrontal area where chemosensory, visual, and spatial information converges. The APC(VR) also has di- and tri-synaptic projections to the VLO via the pEn and the submedial thalamic nucleus. The pEn is of particular interest from a pathological standpoint because it corresponds in location to the physiologically defined "deep piriform cortex" ("area tempestas") from which convulsants initiate temporal lobe seizures, and blockade reduces ischemic damage to the hippocampus. Immunostaining revealed novel features of the pEn and APC(VR) that could alter excitability, including a near-absence of gamma-aminobutyric acid (GABA)ergic "cartridge" endings on axon initial segments, few cholecystokinin (CCK)-positive basket cells, and very low gamma-aminobutyric acid transporter-1 (GAT1)-like immunoreactivity. Normal functions of the APC(VR)-pEn may require a shaping of neuronal activity by inhibitory processes in a fashion that renders this region susceptible to pathological behavior.

Animals↗
PubMed2001

Local differences in vagal afferent innervation of the rat esophagus are reflected by neurochemical differences at the level of the sensory ganglia and by different brainstem projections.

The objective of the present study was to characterize further the vagal afferent fibers in the rat esophagus, particularly those in its uppermost part, their cell bodies in vagal sensory ganglia, and their central projections. We applied immunohistochemistry for calretinin, calbindin, and calcitonin gene-related peptide (CGRP); retrograde tracing with FluoroGold; and transganglionic tracing with wheat germ agglutinin-horseradish peroxidase in combination with neurectomies. Vagal terminal structures in the muscularis propria of the whole esophagus consisted of calretinin-immunoreactive intraganglionic laminar endings that were linked to cervical vagal and recurrent laryngeal nerve pathways. The mucosa of the uppermost esophagus was innervated by a very dense net of longitudinally arranged, calretinin-positive fibers that were depleted by section of the superior laryngeal nerve. Distal to this area, the mucosa was virtually devoid of calretinin-immunoreactive vagal afferents. Calretinin-positive mucosal fibers in the upper cervical esophagus were classified into four types. One type, the finger-like endings, was sometimes immunoreactive also for CGRP. About one-third of cell bodies in vagal sensory ganglia retrogradely labeled from the upper cervical esophagus expressed CGRP, whereas two-thirds coexpressed calretinin and calbindin but not CGRP. In addition to the central subnucleus of the nucleus of the solitary tract, vagal afferents from the upper cervical esophagus also projected heavily to the interstitial subnucleus. This additional projection was attributed to mucosal afferents traveling through the superior laryngeal nerve. The present study provides a possible morphological basis for bronchopulmonary and aversive reflexes elicited upon stimulation of the esophagus.

Animals↗
PubMed2004

GABAergic basal forebrain neurons that express receptor for neurokinin B and send axons to the cerebral cortex.

Neurons expressing neurokinin B (NK3) receptor in the basal forebrain region of rats were characterized histochemically by combining immunocytochemistry, in situ hybridization and retrograde labeling, and electrophysiologically by whole-cell clamp recording. NK3 receptor-immunoreactive neurons were found in the basal forebrain region including the substantia innominata, where axon terminals immunoreactive for preprotachykinin B, the precursor peptide of neurokinin B (NKB), were densely distributed. More than 90% of NK3 receptor-expressing neurons in the basal forebrain region showed signals for glutamate decarboxylase mRNA, indicating that almost all NK3 receptor-expressing neurons were gamma-aminobutyric acid (GABA)ergic neurons. On the other hand, only a few NK3 receptor-immunoreactive neurons showed immunoreactivity for choline acetyltransferase or parvalbumin in the substantia innominata, ventral pallidum, and globus pallidus, although the distribution of NK3 receptor-expressing neurons overlapped with those of cholinergic neurons and parvalbumin-positive neurons. After injection of wheat germ agglutinin into the cerebral cortex, NK3 receptor immunoreactivity was detected in about 25% of retrogradely labeled basal forebrain neurons, indicating that NK3 receptor-expressing neurons send projection fibers to the cerebral cortex. In the whole-cell clamp recording study, a selective NK3 receptor agonist evoked membrane depolarization or inward currents with decrease of input impedance in 10 of 100 cortically projecting neurons recorded in the basal forebrain region. Because NKB-producing striatal neurons send axons selectively to the basal forebrain region, the present results suggest that the release of NKB by those striatal neurons induces an inhibitory effect on cortical neurons via facilitation of GABAergic basal forebrain neurons expressing NK3 receptor.

Animals↗
PubMed2004

Development of the human motor-related thalamic nuclei during the first half of gestation, with special emphasis on GABAergic circuits.

This study analyzed the expression of differentiation markers (Calbindin D28K: CaBP; parvalbumin: PARV; calretinin: CalR), gamma-aminobutyric acid (GABA) markers (GABA, glutamic acid decarboxylases: GAD65, GAD67; and GABA transporters: GAT1, GAT3), and other markers (neurotensin: NT, and neurofilament-specific protein: SMI32) in the human thalamus at 8-23 gestation weeks (g.w.), focusing on the motor-related nuclei. From 8-13 g.w. mainly CaBP was expressed in the cells while fiber bundles traversing the thalamus in addition to CaBP expressed all GABA markers except GAD67. CaBP and PARV expression patterns in different nuclei changed over the time course studied, whereas NT was expressed consistently along the anterior-lateral curvature of the thalamus. CalR and SMI were detectable at 23 g.w. in the ventral parts of the dorsal thalamus. Most remarkably, punctate GAD65 immunoreactivity in the neuropil was confined to the nigro- and pallidothalamic afferent receiving nuclei from 16 to about 21 g.w., overlapping with that of CaBP in some of these nuclei (subdivisions of the ventral anterior and mediodorsal nuclei) and with PARV in others (centromedian nucleus). During this period, GAD65 immunoreactivity can be considered a marker of the basal ganglia afferent receiving territory in the motor thalamus. GAD67-positive local circuit neurons were first detected at 12-13 g.w. in the thalamic nuclei outside the basal ganglia afferent receiving territory. In the ventral anterior and centromedian nuclei, GAD-containing local circuit neurons were not conspicuous even at 22-23 g.w. The cells of the reticular nucleus expressed GAD67 and PARV from 12 g.w. on starting in the lateral-posterior regions. By 23 g.w., both markers were expressed in about two-thirds of the nucleus except for its most medial-anterior part. The results imply spatially and temporally differential expression of GABA and differentiation markers in the developing human thalamus.

Biomarkers↗
PubMed2004

Laminar organization of the mouse dentate gyrus: insights from BETA2/Neuro D mutant mice.

The dentate gyrus of rodents is characterized by a highly laminar organization: above a compact granule cell layer, commissural/associational (C/A) fibers terminate on proximal granule cell dendrites and entorhinal fibers terminate on distal granule cell dendrites in a nonoverlapping manner. To gain insights into mechanisms that underlie the formation of this laminar structure, we studied mice deficient for BETA2/NeuroD, a basic helix-loop-helix transcription factor essential for granule cell differentiation. Anterograde tracing was used to label C/A and entorhinal fibers and combined with confocal double immunofluorescence for calbindin, calretinin, parvalbumin, and reelin to visualize putative target cells. The dentate gyrus of mutant mice contained only few granule cells, which formed a cap-like structure adjacent to area CA3. Despite the severe hypoplasia of the dentate gyrus, the remaining BETA2/NeuroD-deficient granule cells expressed mature markers, extended dendrites into the molecular layer, and extended mossy fibers into area CA3. Entorhinal and C/A fibers terminated in a nonoverlapping manner in the dendritic field overlying the rudiment. Entorhinal fibers terminated in the outermost portion of the dentate gyrus where they surrounded reelin-positive Cajal-Retzius cells, and C/A fibers terminated above and within the dentate rudiment. The laminar termination of C/A fibers was closest to normal in zones of the rudiment in which granule cells were densely packed. These data indicate that granule cells are able to differentiate in the absence of BETA2/NeuroD and suggest that the signals underlying the laminar anatomy of the dentate gyrus are present in the absence of most target cells.

Animals↗
PubMed2005

Embryonic and postnatal development of GABA, calbindin, calretinin, and parvalbumin in the mouse claustral complex.

We analyzed the development of immunoreactive expression patterns for the neurotransmitter gamma-aminobutyric acid (GABA) and the calcium-binding proteins calbindin, calretinin, and parvalbumin in the embryonic and postnatal mouse claustral complex. Each calcium-binding protein shows a different temporal and spatial pattern of development. Calbindin-positive cells start to be seen very early during embryogenesis and increase dramatically until birth, thus becoming the most abundant cell type during embryonic development, especially in the ventral pallial part of the claustrum. The distribution of calbindin neurons throughout the claustrum during embryonic development partly parallels that of GABA neurons, suggesting that at least part of the calbindin neurons of the claustral complex are GABAergic and originate in the subpallium. Parvalbumin cells, on the other hand, start to be seen only postnatally, and their number then increases while the density of calbindin neurons decreases. Based on calretinin expression in axons, the core/shell compartments of the dorsal claustrum start to be clearly seen at embryonic day 18.5 and may be related to the development of the thalamoclaustral input. Comparison with the expression of Cadherin 8, a marker of the developing dorsolateral claustrum, indicates that the core includes a central part of the dorsolateral claustrum, whereas the shell includes a peripheral area of the dorsolateral claustrum, plus the adjacent ventromedial claustrum. The present data on the spatiotemporal developmental patterns of several subtypes of GABAergic neurons in the claustral complex may help for future studies on temporal lobe epilepsies, which have been related to an alteration of the GABAergic activity.

Animals↗
PubMed2005

Immunocytochemical identification of cell types in the mormyrid electrosensory lobe.

The electrosensory lobes (ELLs) of mormyrid and gymnotid fish are useful sites for studying plasticity and descending control of sensory processing. This study used immunocytochemistry to examine the functional circuitry of the mormyrid ELL. We used antibodies against the following proteins and amino acids: the neurotransmitters glutamate and gamma-aminobutyric acid (GABA); the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD); GABA transporter 1; the anchoring protein for GABA and glycine receptors, gephyrin; the calcium binding proteins calbindin and calretinin; the NR1 subunit of the N-methyl-D-aspartate glutamate receptor; the metabotropic glutamate receptors mGluR1alpha, mGluR2/3, and mGluR5; and the intracellular signaling molecules calcineurin, calcium calmodulin kinase IIalpha (CAMKIIalpha) and the receptor for inositol triphosphate (IP3R1alpha). Selective staining allowed for identification of new cell types including a deep granular layer cell that relays sensory information from primary afferent fibers to higher order cells of ELLS. Selective staining also allowed for estimates of relative numbers of different cell types. Dendritic staining of Purkinje-like medium ganglion cells with antibodies against metabotropic glutamate receptors and calcineurin suggests hypotheses concerning mechanisms of the previously demonstrated synaptic plasticity in these cells. Finally, several cell types including the above-mentioned granular cells, thick-smooth dendrite cells, and large multipolar cells of the intermediate layer were present in the two zones of ELL that receive input from mormyromast electroreceptors but were absent in the zone of ELL that receives input from ampullary electroreceptors, indicating markedly different processing for these two types of input. J. Comp. Neurol. 483:124-142, 2005. (c) 2005 Wiley-Liss, Inc.

Animals↗
PubMed2005

Effects of GABAergic transmissions on the immunoreactivities of calcium binding proteins in the gerbil hippocampus.

Although reduced calcium binding protein (CBP) immunoreactivities in the epileptic hippocampus have been well established, it has been controversial that these changes may directly indicate neuronal degeneration. In the present study, therefore, we investigated CBP expressions in the gerbil hippocampus following treatment with gamma-aminobutyric acid (GABA) receptor antagonists in order to assess whether altered CBP expressions are the result of either abnormal excitation or indicative of neuronal damage/degeneration. Seizure-sensitive (SS) gerbils showed a loss/decline of CBP immunoreactivities in some hippocampal neurons as compared with seizure-resistant (SR) gerbils. In muscimol (GABA(A) receptor agonist) treated SS gerbils, expression levels of CBP were enhanced as compared with saline-treated SS gerbils. Bicuculline (a GABA(A) receptor antagonist) treatment markedly reduced CBP immunoreactivities in hippocampal neurons of the SR gerbil. Baclofen (a GABA(B) receptor agonist) treatment increased CBP immunoreactivities in the hippocampus of SS gerbils, although its effect was lower than that of muscimol treatment. Moreover, phaclofen (GABA(B) receptor antagonist) treated SR gerbil showed reduction in calbindin D-28K immunoreactivity, not parvalbumin immunoreactivity, in the hippocampus. These findings therefore suggest that reduced CBP immunoreactivities may be the consequence of abnormal discharge caused by loss of GABAergic inhibition rather than an indication of the neuronal damage/degeneration.

Animals↗
PubMed2005

Localization of glycine receptor alpha subunits on bipolar and amacrine cells in primate retina.

The major inhibitory neurotransmitter glycine is used by about half of the amacrine cells in the retina. Amacrine cells provide synaptic output to bipolar, ganglion, and other amacrine cells. The present study investigated whether different bipolar and amacrine cell types in the primate retina differ with respect to the expression of glycine receptor (GlyR) subtypes. Antibodies specific for the alpha1, alpha2, and alpha3 subunits of the GlyR were combined with immunohistochemical markers for bipolar and amacrine cells and applied to vertical sections of macaque (Macaca fascicularis) and marmoset (Callithrix jacchus) retinae. For all subunits, punctate immunoreactivity was expressed in the inner plexiform layer. The GlyRalpha2 immunoreactive (IR) puncta occur at the highest density, followed by GlyR(alpha)3 and GlyR(alpha)1 IR puncta. Postembedding electron microscopy showed the postsynaptic location of all subunits. Double immunofluorescence demonstrated that the three alpha subunits are clustered at different postsynaptic sites. Two OFF cone bipolar cell types (flat midget and diffuse bipolar DB3), are predominantly associated with the alpha1 subunit. Two ON bipolar cell types, the DB6 and the rod bipolar cell, are predominantly associated with the alpha2 subunit. The glycinergic AII amacrine cell is presynaptic to the alpha1 subunit in the OFF-sublamina, and postsynaptic to the alpha2 subunit in the ON-sublamina. Another putative glycinergic cell, the vesicular glutamate transporter 3 cell, is predominantly presynaptic to the alpha2 subunit. The dopaminergic amacrine cell expresses the alpha3 subunit at a low density.

Amino Acid Transport Systems, Acidic↗