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PubMed2004

Definition and connections of the entopallium in the zebra finch (Taeniopygia guttata).

In birds the entopallium (formerly known as the core region of ectostriatum) is the major thalamorecipient zone, within the telencephalon, of the tectofugal visual system. Here we sought to redefine the entopallium in the zebra finch, particularly with respect to a laterally adjacent zone, known as the perientopallium (formerly known as the periectostriatal belt), and to determine its projections. We show that the entopallium can be defined by the almost complete overlap of dense terminations of thalamic rotundal afferents and intense cytochrome oxidase activity and parvalbumin immunoreactivity. The perientopallium, on the other hand, can be defined by relatively sparse projections from nucleus rotundus, a calretinin-positive plexus of nerve fibers, and weak cytochrome oxidase activity and parvalbumin immunoreactivity. Within the entopallium, medial and lateral parts can be distinguished on the basis of cell packing density, differential patterns of parvalbumin immunoreactivity and cytochrome oxidase activity, and different projections. We show that the entopallium projects laterally and diffusely to the perientopallium and nidopallium (formerly the neostriatum) and specifically and densely to a teardrop-shaped nucleus in the ventrolateral mesopallium (formerly known as the hyperstriatum ventrale), here called MVL (abbreviation used as a proper name). This latter projection arises predominantly from medial parts of the entopallium, which also receives a reciprocal projection from MVL, and projects to the lateral striatum. These findings suggest that the entopallium can be divided into medial and lateral parts having different functions, one of which is to provide for an extratelencephalic outflow from the medial part, via the lateral striatum. The findings also challenge the idea that informational flow through the various stations of the telencephalic tectofugal visual system is largely sequential and, together with findings in the chicken (Alpar and Tömböl), suggest instead that further substantial projections to telencephalic visual areas in birds can arise independently from both E (entopallium) and Ep (perientopallial belt).

Animals↗

PubMed2004

Neurogenesis and stereological morphometry of calretinin-immunoreactive GABAergic interneurons of the neostriatum.

We determined the neurogenesis characteristics of a distinct subclass of rat striatum gamma-aminobutyric acidergic (GABAergic) interneurons expressing the calcium-binding protein calretinin (CR). Timed-pregnant rats were given an intraperitoneal injection of 5-bromo-2'-deoxyuridine (BrdU), a marker of cell proliferation, on designated days between embryonic day 12 (E12) and E21. CR-immunoreactive (-IR) neurons and BrdU-positive nuclei were labeled in the adult neostriatum by double immunohistochemistry, and the proportion of double-labeled cells was quantified. CR-IR interneurons of the neostriatum show maximum birth rates (>10% double labeling) between E14 and E17, with a peak at E15. CR-IR interneurons occupying the lateral half of the neostriatum become postmitotic prior to medial neurons. In the precomissural neostriatum, the earliest-born neurons occupy the lateral quadrants and the latest-born neurons occupy the dorsomedial sector. No significant rostrocaudal neurogenesis gradient is observed. CR-IR neurons make up 0.5% of the striatal population and are localized in both the patch and the matrix compartments. CR-IR neurons of the patch compartment are born early (E13-15), with later-born neurons (E16-18) populating mainly the matrix compartment. CR-IR cells of the neostriatum are a distinct subclass of interneurons that are born at an intermediate time during striatal development and share common neurogenesis characteristics with other interneurons and projection neurons produced in the ventral telencephalon.

Age Factors↗

PubMed2004

Synaptic connectivity of the diffuse bipolar cell type DB6 in the inner plexiform layer of primate retina.

Diffuse bipolar cells in primate retina receive synaptic input from multiple cones and provide output to ganglion cells. Diffuse bipolar cells can be subdivided into six types (DB1-DB6) according to the stratification of their axon terminals in the inner plexiform layer, but their synaptic connectivity in the inner plexiform layer is not well understood. Here the stratification and synaptic connectivity of DB6 axon terminals were studied in the retinae of New World (marmoset) and Old World (macaque) monkeys. Immunohistochemical markers were applied to retinal sections. The sections were analyzed by confocal and deconvolution light microscopy as well as electron microscopy. The DB6 cells were identified with antibodies against CD15; rod bipolar cells were identified with antibodies against protein kinase Calpha (PKCalpha); and AII amacrine cells were identified with antibodies against calretinin. The axons of DB6 and rod bipolar cells occupy distinct regions in stratum 5 of the inner plexiform layer. The distal processes of calretinin-labeled AII cells are usually closely associated with rod bipolar axons but sometimes also with DB6 axons. Pre-embedding immunoelectron microscopy showed that the vast majority (over 86%) of the synaptic output of DB6 cells is onto amacrine cell processes, whereas less than 14% goes to ganglion cell processes. In double-labeled preparations DB6 axons occasionally made output onto calretinin-labeled amacrine processes. Thus it is possible that AII cells receive some input from DB6 cells.

Amacrine Cells↗

PubMed2001

Coupling from AII amacrine cells to ON cone bipolar cells is bidirectional.

The AII amacrine cell is a critical interneuron in the rod pathway of the mammalian retina. Rod signals pass into cone pathways by means of gap junctions between AII amacrine cells and ON cone bipolar cells. Filling AII amacrine cells with Neurobiotin produces labeling of cone bipolar cells by means of these gap junctions. However, tracer injections into bipolar cells do not produce labeling of the AII network (Vaney [1997] Invest Ophthalmol Vis Sci. 38:267-273), which suggests that the AII/bipolar gap junctions allow the passage of tracer in only one direction. This mechanism stands in contrast to physiological results, which indicate that light adapted signals can pass from ON cone bipolar cells into the AII network (Xin and Bloomfield [1999] Vis Neurosci. 16:653-665). Here, we report that a variety of ON and OFF bipolar cells are sometimes anomalously coupled to the A-type horizontal cell network. These relatively rare examples do not result from dye injection errors, but seem to represent minor developmental errors. However, this provides a method to obtain Neurobiotin-filled cone bipolar cells without the necessity of impaling them with a microelectrode. Under these conditions, Neurobiotin spreads from ON cone bipolar cells into neighboring AII amacrine cells. The dye-coupled AII amacrine cells, positively identified by double labeling with an antibody against calretinin, were centered around anomalously coupled ON bipolar cells. These results indicate that AII/bipolar cell gap junctions allow tracer coupling in both directions, consistent with previous physiological results. The previous failure to detect the passage of neuronal tracer from injected bipolar cells to AII amacrine cells may reflect electrode damage or perhaps the asymmetrical voltage sensitivity of a heterotypic gap junction.

Animals↗

PubMed2001

Organisation and maturation of the human thalamus as revealed by CD15.

The distribution of the CD15 antigen (CD15, 3-fucosyl-N-acetyl-lactosamine, Lewis x) has been studied immunohistochemically in the fetal human thalamus. Its changing patterns could be related to three successive, but overlapping, periods primarily due to its association with radial glial cells, neuropil, and neural cell bodies, respectively. From 9 weeks of gestation (wg), a subset of CD15-positive radial glial cells distinguished the neuroepithelium of the ventral thalamus, a characteristic also seen in the developing mouse. Distal processes of the radial glial cells converged at the root of the forebrain choroid tenia, which was also CD15 positive. From 13 wg until approximately 20 wg, CD15-positive neuropil labeling marked the differentiation areas of prospective nuclei within the dorsal thalamus and progressively outlined their territories in a time sequence, which appeared specific for each nucleus. CD15 labeling of differentiating nuclei of the ventral, medial, anterior, and intralaminar thalamic divisions showed a transient topographic relationship with restricted areas of the ventricular wall. After 26 wg, CD15 immunoreactivity was observed in subpopulations of glial cells and neurons. Transient CD15 immunoreactivity was also found in delimited compartments within the subventricular region. The time of CD15 expression, its location, and cellular association suggest that CD15 is involved in segmentation of diencephalon, in the specification of differentiating nuclear areas and initial processes regarding the formation of intercellular contacts and cellular maturation.

Biomarkers↗

PubMed2001

Stereological estimates of total neuron numbers in the hippocampus of adult reeler mutant mice: Evidence for an increased survival of Cajal-Retzius cells.

The cytoarchitecture of the brain is disrupted severely in reeler mice. This is caused by a deficiency in the protein, Reelin, which is essential for the normal migration and positioning of neurons during development. Although cell migration is clearly affected by the reeler mutation, it is believed that the total number of neurons is not. Thus, we were surprised to find an unusually large number of calretinin-immunopositive cells, presumably Cajal-Retzius cells, in the molecular layer of the adult reeler hippocampus (Deller et al. [1999]; Exp. Neurol. 156:239-253). This suggested that the reeler mutation affects the number of neurons in the hippocampus. In order to verify this hypothesis, unbiased stereological methods were employed. Calretinin immunostaining was used as a marker for Cajal-Retzius cells in control as well as reeler mice and Nissl staining was used to identify hippocampal principal neurons. Total numbers of calretinin-immunopositive cells, calretinin-immunoreactive Cajal-Retzius cells, and Nissl-stained neurons were estimated in different subfields of the reeler and the control hippocampus. Stereological estimates (P < 0.05) revealed that the total number of calretinin-immunopositive and Cajal-Retzius cells in reeler mice are 1.5 and 2.1 times that of controls, respectively. No significant difference in total neuron number was found in any hippocampal subfield. These data demonstrate that the reeler mutation affects the number of calretinin-immunoreactive Cajal-Retzius cells in the adult hippocampus, probably due to a reduced excitatory innervation by entorhinal terminals in the absence of reelin. However, the reeler mutation does not affect mechanisms that determine total hippocampal neuron number.

Animals↗

PubMed2001

Commissurally projecting inhibitory interneurons of the rat hippocampal dentate gyrus: a colocalization study of neuronal markers and the retrograde tracer Fluoro-gold.

Improved methods for detecting neuronal markers and the retrograde tracer Fluoro-Gold (FG) were used to identify commissurally projecting neurons of the rat hippocampus. In addition to the dentate hilar mossy cells and CA3 pyramidal cells shown previously to transport retrograde tracers after injection into the dorsal hippocampus, FG-positive interneurons of the dentate granule cell layer and hilus were detected in numbers greater than previously reported. FG labeling of interneurons was variable among animals, but was as high as 96% of hilar somatostatin-positive interneurons, 84% of parvalbumin-positive cells of the granule cell layer and hilus combined, and 33% of hilar calretinin-positive cells. By comparison, interneurons of the dentate molecular layer and all hippocampal subregions were conspicuously FG-negative. Whereas hilar mossy cells and CA3 pyramidal cells were FG-labeled throughout the longitudinal axis, FG-positive interneurons exhibited a relatively homotopic distribution. "Control" injections of FG into the neocortex, septum, and ventral hippocampus demonstrated that the homotopic labeling of dentate interneurons was injection site-specific, and that the CA1-CA3 interneurons unlabeled by contralateral hippocampal FG injection were nonetheless able to transport FG from the septum. These data suggest a hippocampal organizing principle according to which virtually all commissurally projecting hippocampal neurons share the property of being monosynaptic targets of dentate granule cells. Because granule cells innervate their exclusively ipsilateral target cells in a highly lamellar pattern, these results suggest that focal granule cell excitation may result in commissural inhibition of the corresponding "twin" granule cell lamella, thereby lateralizing and amplifying the influence of the initiating discharge.

Animals↗

PubMed2004

Parvalbumin-containing interneurons in the basolateral amygdala express high levels of the alpha1 subunit of the GABAA receptor.

The basolateral amygdala (ABL) is essential for the amnestic effects of benzodiazepines in aversive learning tasks. Because the alpha1 subunit of the gamma-aminobutyric acid (GABA)(A) receptor is critical for these amnestic actions, knowledge of the neuronal localization of this subunit in the ABL should contribute to an understanding of the candidate neuronal mechanisms involved. To examine this question, we used dual-labeling immunohistochemical techniques to study the localization of the alpha1 subunit in the ABL. Our results suggest that the alpha1 subunit of the GABA(A) receptor is localized primarily in GABAergic interneurons in the ABL at the somal level, although the intense neuropil staining in the lateral nucleus suggests that distal dendrites of pyramidal projection neurons in this nucleus may also contain high levels of the alpha1 subunit. The great majority of alpha1-immunoreactive interneurons also exhibit immunoreactivity for the beta2/3 subunits of the GABA(A) receptor. Parvalbumin-positive (PV+) interneurons are the main interneuronal subpopulation exhibiting alpha1 immunoreactivity, but some calretinin-positive interneurons also express this subunit. These data suggest that certain subpopulations of GABAergic interneurons in the ABL, especially PV+ cells, receive a robust GABAergic innervation. Because the most likely source of this innervation is intrinsic, these results suggest that PV+ interneurons could constitute an important component of interneuronal networks in the ABL. These networks may be critical for the generation of synchronized rhythmic oscillations involved in consolidation of emotional memories. The activation of alpha1-containing GABA(A) receptors in the ABL by benzodiazepines may disrupt rhythmic oscillations critical for memory consolidation.

Amygdala↗

PubMed2004

Somatomotor system of the adult amphioxus (Branchiostoma lanceolatum) revealed by an anticalretinin antiserum: An immunocytochemical study.

In a classic study with silver staining methods, the somatomotor system of the amphioxus spinal cord was described as consisting of three different types of neuron segmentally arranged in two opposite fan-shaped group types (Bone [1960] J Comp Neurol 115:27-64). The present study reports the presence of calretinin-like immunoreactivity in the somatomotor system of the amphioxus, which allows us to reevaluate old descriptions of amphioxus motoneurons. In the spinal cord, two types of calretinin-like immunoreactive (CR-ir) motoneurons, large and small, sent processes toward the ventrolateral region of the cord, where they branched and gave rise to processes coursing longitudinally in the somatomotor bundles. These processes produced a number of long and thin collaterals directed to several neuropil regions. Short collaterals were directed to the region of the neuromuscular contacts at the ventrolateral surface of the cord. The groups of CR-ir motoneurons exhibited a segmental organization and were localized only facing the myomeres, i.e., opposite to the entrance of the dorsal nerve roots, which is at variance with the above-mentioned classical report. CR-ir motoneurons were also observed in the brain between a level just rostral to the nerve III entry and nerve VI. The CR-ir somatomotor bundle ascended to the region of the neuromuscular junction of myomere 1. Additional faintly CR-ir neurons were observed in the region of the lamellate body of the brain. Our results reveal for the first time that calretinin immunoreactivity in the central nervous system of amphioxus was limited to a few types of neuron and that calretinin was not expressed in the peripheral nervous system, unlike vertebrates.

Animals↗

PubMed2006

Calretinin immunoreactivity in the brain of the zebrafish, Danio rerio: distribution and comparison with some neuropeptides and neurotransmitter-synthesizing enzymes. I. Olfactory organ and forebrain.

The distribution of calretinin (CR) in the forebrain and the olfactory system of the adult zebrafish was studied by using immunocytochemical techniques. Previous studies in trout forebrain have indicated that CR-immunoreactive neurons acquire this phenotype rather early in development (Castro et al., J. Comp. Neurol. 467:254-269, 2003). Thus, precise knowledge of CR-expressing neuronal populations in adult zebrafish may help to decipher late stages of forebrain morphogenesis. For analysis of some forebrain nuclei and regions, CR distribution was compared with that of various ancillary markers: choline acetyltransferase, glutamic acid decarboxylase, tyrosine hydroxylase, neuropeptide Y, thyrotropin-releasing hormone, and galanin. The results reveal that calretinin is a specific marker of olfactory receptor neurons and of various neuronal populations distributed throughout the telencephalon and diencephalon. In addition, CR immunocytochemistry revealed characteristic patterns of fibers and neuropil in several telencephalic and diencephalic regions, indicating that it is a useful marker for characterizing a number of neural centers, pathways, and neuronal subpopulations in the zebrafish forebrain. Some ancillary markers also showed a distinctive distribution in pallial and subpallial regions, revealing additional aspects of forebrain organization. Comparison of the distribution of CR observed in the forebrain of zebrafish with that reported in other teleosts revealed a number of similarities and also some interesting differences. This indicates that various neuronal populations have maintained the CR phenotype in widely divergent teleost lines and suggests that CR studies may prove very useful for comparative analysis.

Animals↗

PubMed2006

Calretinin immunoreactivity in the brain of the zebrafish, Danio rerio: distribution and comparison with some neuropeptides and neurotransmitter-synthesizing enzymes. II. Midbrain, hindbrain, and rostral spinal cord.

The distribution of calretinin (CR) in the brainstem and rostral spinal cord of the adult zebrafish was studied by using immunocytochemical techniques. For analysis of some brainstem nuclei and regions, CR distribution was compared with that of complementary markers (choline acetyltransferase, glutamic acid decarboxylase, tyrosine hydroxylase, neuropeptide Y). The results reveal that CR is a marker of various neuronal populations distributed throughout the brainstem, including numerous cells in the optic tectum, torus semicircularis, secondary gustatory nucleus, reticular formation, somatomotor column, gustatory lobes, octavolateral area, and inferior olive, as well as of characteristic tracts of fibers and neuropil. These results indicate that CR may prove useful for characterizing a number of neuronal subpopulations in zebrafish. Comparison of the distribution of CR observed in the brainstem of zebrafish with that reported in an advanced teleost (the gray mullet) revealed a number of similarities, and also some interesting differences. Our results indicate that many brainstem neuronal populations have maintained the CR phenotype in widely divergent teleost lines, so CR studies may prove very useful for comparative analysis.

Animals↗

PubMed2006

Mouse cortical inhibitory neuron type that coexpresses somatostatin and calretinin.

Mammalian cortex contains a diversity of inhibitory neuron types, each with distinct morphological, immunochemical, and/or physiological properties. In rat cortex, chemical markers distinguish at least four distinct and nonoverlapping neuron classes based on expression of parvalbumin (PV), somatostatin (SST), calretinin (CR), and cholecystokinin (CCK). It has generally been assumed that these classifications should also apply to other rodent species. In mouse cortex, however, we found significant colocalization of SST and CR in inhibitory neurons; about 30% of SST-positive cells contained CR, and about 33% of CR-positive cells contained SST across frontal, somatosensory (S1), and visual cortex (V1). The SST and CR colocalized cells were concentrated in layer 2/3. We further characterized morphological and physiological properties of the mouse cortical inhibitory neuron types that express SST by using "GIN" transgenic mice, in which GFP is expressed in a subset of SST inhibitory neurons (see Oliva et al. [2000] J Neurosci 20:3354-3368). Generally, both SST/CR+ cells and SST/CR- cells exhibited morphological features of Martinotti cells as described in rat cortex, and they also had similar accommodating spike-firing patterns. However, they differed significantly in quantitative comparisons of morphology and spike shapes. SST/CR+ cells had more horizontally extended dendritic fields and more primary process than did SST/CR- cells; and SST/CR- cells had narrower action potential widths and faster afterhyperpolarization than did SST/CR+ cells. Thus, our data show an important species difference in the chemical distinction of inhibitory neuron subtypes, and indicate that colocalization of CR in SST cells correlates with different morphological and physiological features.

Action Potentials↗

PubMed2006

Presence of glutamate, glycine, and gamma-aminobutyric acid in the retina of the larval sea lamprey: comparative immunohistochemical study of classical neurotransmitters in larval and postmetamorphic retinas.

The neurochemistry of the retina of the larval and postmetamorphic sea lamprey was studied via immunocytochemistry using antibodies directed against the major candidate neurotransmitters [glutamate, glycine, gamma-aminobutyric acid (GABA), aspartate, dopamine, serotonin] and the neurotransmitter-synthesizing enzyme tyrosine hydroxylase. Immunoreactivity to rod opsin and calretinin was also used to distinguish some retinal cells. Two retinal regions are present in larvae: the central retina, with opsin-immunoreactive photoreceptors, and the lateral retina, which lacks photoreceptors and is mainly neuroblastic. We observed calretinin-immunostained ganglion cells in both retinal regions; immunolabeled bipolar cells were detected in the central retina only. Glutamate immunoreactivity was present in photoreceptors, ganglion cells, and bipolar cells. Faint to moderate glycine immunostaining was observed in photoreceptors and some cells of the ganglion cell/inner plexiform layer. No GABA-immunolabeled perikarya were observed. GABA-immunoreactive centrifugal fibers were present in the central and lateral retina. These centrifugal fibers contacted glutamate-immunostained ganglion cells. No aspartate, serotonin, dopamine, or TH immunoreactivity was observed in larvae, whereas these molecules, as well as GABA, glycine, and glutamate, were detected in neurons of the retina of recently transformed lamprey. Immunoreactivity to GABA was observed in outer horizontal cells, some bipolar cells, and numerous amacrine cells, whereas immunoreactivity to glycine was found in amacrine cells and interplexiform cells. Dopamine and serotonin immunoreactivity was found in scattered amacrine cells. Amacrine and horizontal cells did not express classical neurotransmitters (with the possible exception of glycine) during larval life, so transmitter-expressing cells of the larval retina appear to participate only in the vertical processing pathway.

Animals↗

PubMed2007

Morphological and physiological properties of parvalbumin- and calretinin-containing gamma-aminobutyric acidergic neurons in the substantia nigra.

Evidence for the existence of different populations of gamma-aminobutyric acid (GABA)-ergic neurons in the substantia nigra comes partially from anatomical studies, which have shown there to be little if any overlap between the calcium-binding proteins parvalbumin and calretinin in individual neurons, suggesting that these may represent neuronal subtypes with distinct electrophysiological and/or anatomical properties. We obtained whole-cell recordings from neurons in the substantia nigra pars reticulata in rat brain slices and labeled them with biocytin, followed by immunocytochemical staining for parvalbumin and calretinin. In other cases, neurons were retrogradely labeled from the thalamus or tectum and immunocytochemically identified to determine their projection sites. Intracellularly stained neurons were found to have a variety of somatic sizes and shapes. Reconstructions revealed that all parvalbumin- and calretinin-positive neurons issued at least one axon collateral, which ramified within the substantia nigra pars reticulata and/or pars compacta. Local collaterals were of medium caliber and branched modestly, expressing many long, smooth segments that then issued numerous en passant or terminal boutons, consistent with previous in vivo studies. There were no clear differences in the electrophysiological or morphological properties of neurons expressing parvalbumin or calretinin. Retrograde tracing experiments revealed that both parvalbumin- and calretinin-containing neurons project nonpreferentially to the thalamus or tectum. In sum, the parvalbumin- and calretinin-containing GABAergic neurons of the substantia nigra pars reticulata cannot be differentiated on the basis of their electrophysiological properties, morphological properties, or target nuclei, and both parvalbumin- and calretinin-containing projection neurons issue local axon collaterals that arborize within the substantia nigra.

Animals↗

PubMed2007

Functional activation of glutamate ionotropic receptors in the developing mouse retina.

Ionotropic glutamate receptors have been associated with early development of the visual process by regulating cell differentiation, cell motility, and synaptic contacts. We determined the expression of functional ionotropic glutamate receptors during development of the mouse retina by assessing 1-amino-4-guanidobutane (agmatine; AGB) immunolabelling after application of a range of glutamate analogs. Colocalization of AGB with calretinin and islet-1 allowed the identification of functional receptors in neurochemically defined neurons. Activation with kainate (KA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA) resulted in AGB entry into neurons consistent with that found previous receptor subunit localization studies in the developing retina. Temporal analysis revealed that application of 50 microM KA activated receptors as early as embryonic day 18 in the ventricular zone and in the ganglion cell layer, whereas 30 muM AMPA activated cells predominantly in the ganglion cell layer. Cholinergic amacrine cells showed functional KA and AMPA receptors upon their insertion into the conventional amacrine cell layer from postnatal day 1 (P1). OFF cone bipolar cells showed functional KA receptors from P6, at a developmental age when they are known to make contact with ganglion cells. NMDA activation led to diffuse AGB labeling at birth among cells in the ganglion cell layer, whereas, at P1, regularly spaced cholinergic amacrine cells in the conventional amacrine cell layer started to be responsive to NMDA. Non-NMDA receptors were first to show functional activation in the developing retina, and cholinergic amacrine cells displayed functional ionotropic glutamate receptors after reaching their final destination.

Animals↗

PubMed1991

Immunocytochemical localization of calretinin in the forebrain of the rat.

The distribution of the calcium binding protein calretinin (protein 10) was examined in the rat forebrain by immunohistochemistry. The main and accessory olfactory bulbs had immunoreactive label in granule, periglomerular, and mitral cells. Positive fibers were noted in the external plexiform and granule cell layers, glomeruli, and in the molecular layer of the anterior olfactory nucleus. The cerebral cortex contained calretinin label in nonpyramidal bipolar cells. Cells in the substantia nigra compacta and ventral tegmental area were also calretinin positive as were nigrostriatal and mesolimbic projections (caudate-putamen, nucleus accumbens). In the hippocampus, interneurons were stained in all the subfields of the CA1-CA4 regions. In the thalamus, many positive cells were observed in the periventricular, reticular, lateral habenula, and reunions nuclei. Calretinin immunoreactive cells were particularly abundant in the lateral mamillary and septofimbrial nuclei. Several fiber tracts were also revealed, i.e., the lateral olfactory tract, mamillothalamic tract, fasciculus retroflexus, optic tract, and stria medullaris. These results demonstrate a distinct distribution of calretinin within cell bodies and fibers.

Animals↗

PubMed1991

Immunohistochemical localization of calretinin in the rat hindbrain.

The localization of calretinin in the rat hindbrain was examined immunohistochemically with antiserum against calretinin purified from the guinea pig brain. Calretinin immunoreactivity was found within neuronal elements. The distribution of calretinin-immunoreactive cell bodies and fibers is presented in schematic drawings and summarized in a table. Major calretinin-immunoreactive neurons were found in the lateral and medial geniculate nuclei, substantia nigra, ventral tegmental area, interpeduncular nucleus, periaqueductal gray, mesencephalic trigeminal nucleus, superior and inferior colliculi, pontine nuclei, parabrachial nucleus, dorsal and laterodorsal tegmental nuclei, cochlear nuclei, vestibular nuclei, medullary reticular nuclei, nucleus of the solitary tract, area postrema, substantia gelatinosa of the spinal trigeminal nucleus, and cerebellum. These results show that distinct calretinin-immunoreactive neurons are widely distributed in the rat hindbrain.

Animals↗

PubMed1994

Development of calretinin immunoreactivity in the mouse inner ear.

Calretinin is a calcium-binding protein of the EF-hand family. It has been previously identified in particular cell types of adult guinea pig, rat, and chinchilla inner ear. Development of calretinin immunoreactivity in the mouse inner ear was investigated from embryonic day 13 (E13) to the adult stage. In the adult mouse vestibule, calretinin immunoreactivity was present in the same structures as described for the rat and guinea pig: the population of afferent fibers forming calyx units and a small number of ganglion neurons. The earliest immunoreactivity was found at E17 in vestibular hair cells (VHCs), then, at E19, in afferent fibers entering the sensory epithelia and in rare ganglion neurons. At postnatal day 4 (P4), a few vestibular nerve fibers and ganglion neurons were reactive. From this stage until P14, immunoreactivity developed in the calyx units and disappeared from VHCs. At P14, immunostaining was adult-like. In the adult mouse cochlea, immunoreactivity was present in the same cell populations as described in the rat: the inner hair cells (IHCs) and most of Corti's ganglion neurons. Calretinin immunoreactivity appeared at E19-P0 in IHCs and ganglion neurons of the basal turn. At P1, outer hair cells (OHCs) of the basal turn were positive. Calretinin immunoreactivity then appeared in IHCs, OHCs, and ganglion neurons of the medial turn, then of the apical turn. At P4, all IHCs and OHCs and most of the ganglion neurons were immunostained. Immunoreactivity gradually disappeared from the OHCs starting at P10 and, at P22, only IHCs and ganglion neurons were positive. The sequences of appearance of calretinin were specific to each cell type of the inner ear and paralleled their respective maturation. Calretinin was transiently expressed in VHCs and OHCs.

Animals↗