Embryonic and postnatal development of calcium-binding proteins immunoreactivity in the anterior thalamus of the guinea pig

Our recent studies have shown that the distribution of calretinin (CR) in the anterior thalamic nuclei (ATN) changes significantly during the development of the guinea pig. The present study was designed to reveal the distribution pattern of calcium-binding proteins, i.e. calbindin (CB) and parvalbumin (PV), as well as the colocalization pattern of all three proteins, including CR, in the ATN of guinea pigs ranging from the 40th embryonic day (E40) to the 80th postnatal day (P80). According to these patterns, CB appears exclusively in the perikarya of the anteromedial nucleus (AM) not before P20 and always colocalizes with CR. Moreover, CB and CR colocalize in fibers of thin bundles traversing the anteroventral nucleus (AV) since E50. The ATN also display CB-positive neuropil in all studied stages, especially a strong one in the ventral part of the AV. PV was not observed in the perikarya of the ATN in all the stages, but was abundantly present in the neuropil of the anterodorsal nucleus (AD). No colocalizations exist between PV and the rest of the studied proteins. In conclusion, our study reveals that the distribution of the studied proteins differs greatly. Nevertheless, the postnatal coexistence of CB and CR in the AM perikarya may indicate the cooperation of both of the proteins in some functions of the nucleus. Parvalbumin is limited mostly to the neuropil of the AD, suggesting different functions in comparison to CB and CR.     

Distribution of calcium-binding protein immunoreactivities in the guinea pig auditory brainstem

This study was intended to provide an overview of the distribution of calcium-binding proteins in the rodent auditory brainstem. We based our observations on immunohistochemical material obtained in the guinea pig, a species widely used in auditory research in which a mapping of calcium-binding proteins in the auditory brainstem is still missing. Differences in the amounts of these proteins throughout the auditory brainstem were further analyzed semiquantitatively. Parvalbumin was present in most neurons and their axon terminals throughout the ascending auditory brainstem. Nuclei that surround the main relay nuclei of the ascending auditory pathway lacked labeling. Calretinin staining was prominent in spherical and globular cells of the cochlear nucleus, in their axon terminals in the superior olivary complex, and in principal cells of the medial superior olive. Measures of optical densities showed that auditory neurons involved in sound localization had the highest calretinin labeling levels. Calbindin D-28k was present in cartwheel cells of the dorsal cochlear nucleus, in almost all neurons of the medial nucleus of the trapezoid body, and in globular cells in the ventral nucleus of the lateral lemniscus. The labeling patterns for calretinin and calbindin D-28k were non-overlapping throughout the auditory brainstem. This was also evident in the ventral nucleus of the lateral lemniscus where calbindin D-28k-immunoreactive terminals were found in the medial portion, while the calretinin-immunoreactive terminals were observed in the lateral portion. This study presents the first direct and comprehensive comparison of these three calcium-binding proteins in the auditory brainstem of a rodent. Each antibody yields a unique staining pattern that provides a basis for further defining neuronal populations. In addition, since their axons are also selectively stained, auditory nuclei can further be compartmentalized based on different terminal fields. These immunoreactivities have provided clues to the complex structure of the auditory brainstem.     

Calcium-binding proteins in the cerebellar cortex of the bottlenose dolphin and harbour porpoise

Studying the distribution of Ca²⁺-binding proteins allows one to discover specific neuron chemotypes involved in the regulation of the activity of various neural elements. While extensive data exist on Ca²⁺-binding proteins in the nervous system, in particular, in the cerebellar cortex of terrestrial mammals, the localization of these proteins in the cerebellar cortex of marine mammals has not been studied. We studied the localization of calretinin, calbindin, and parvalbumin immunoreactivity in the cerebellar cortex of the bottlenose dolphin Tursiops truncates and harbour porpoise Phocoena phocoena. In both species, most Purkinje cells were calbindin-immunoreactive, while calretinin and parvalbumin were expressed in a small portion of Purkinje cells. In addition, calretinin-immunoreactive unipolar brush and granule cells and calbindin- and parvalbumin-immunoreactive basket, stellate, and Golgi cells were observed. Calretinin-immunoreactive corticopetal (mossy and climbing) fibers were found. Based on the length of the primary dendrite, short-, middle-, and long-dendrite unipolar brush cells could be distinguished. The validity of this classification was supported using cluster analysis suggesting the presence of several natural types of these cells. The distribution of Ca²⁺-binding proteins in the cerebellar cortex of the cetaceans studied was generally similar to that reported for terrestrial mammals, suggesting that this trait is evolutionarily conservative in mammals.     

Postnatal development of calcium-binding proteins immunoreactivity (parvalbumin, calbindin, calretinin) in the human entorhinal cortex

The entorhinal cortex is an essential component in the organization of the human hippocampal formation related to cortical activity. It transfers, neocortical information (ultimately distributed to the dentate gyrus and hippocampus) and receives most of the hippocampal output directed to neocortex. At birth, the human entorhinal cortex presents similar layer organization as in adults, although layer II (cell islands) and upper layer III have a protracted maturation. The presence of interneurons expressing calcium-binding proteins (parvalbumin, calbindin–D28K (calbindin) and calretinin) is well documented in the adult human entorhinal cortex. In many of them the calcium binding is co-localized with GABA. Parvalbumin-immunoreactive cells and fibers were virtually absent at birth, their presence increasing gradually in deep layer III, mostly in the lateral and caudal portions of the entorhinal cortex from the 5th month onwards. Calbindin immunoreactive cells and fibers were present at birth, mainly in layers II and upper III; mostly at rostral and lateral portions of the entorhinal cortex, increasing in number and extending to deep layers from the 5th month onwards. Calretinin immunoreactivity was present at birth, homogeneously distributed over layers I, II and upper V, throughout the entorhinal cortex. A substantial increase in the number of calretinin neurons in layer V was observed at the 5th month. The postnatal development of parvalbumin, calbindin and calretinin may have an important role in the functional maturation of the entorhinal cortex through the control of hippocampal, cortical and subcortical information.     

Cortical modulation of thalamo-cortical neurons relaying exteroceptive information: a microstimulation study in the guinea pig

Summary The nature and organization of cortical influences on somatosensory thalamic neurons were investigated in the guinea pig in order to ascertain if mechanisms subserving sensory-motor integration in the thalamus are as precise as has previously been demonstrated in the agranular frontal cortex (AGr) and granular parietal cortex (Gr). The study was carried out on 14 chronically-implanted awake animals. In each experiment one or two motor foci within AGr and Gr were identified according to the region of the movement evoked by intracortical microstimulation at the lowest threshold stimulation (usually 5–15 µA). Spontaneous activity of 182 thalamo-cortical single neurons was recorded in the nucleus ventralis thalami (VT). The neurons were also identified by their response to activation of cutaneous receptive fields (RFs) located in regions of vibrissae or limbs, and then tested for cortical stimulation with a pulse intensity equal to the threshold for evoking motor effects. During the cortico-thalamic tests, the duration of stimulating trains was reduced in order to avoid the appearance of limb or vibrissa movements which could activate somatosensory ascending pathways forwarding peripheral messages to VT. The cortical control on VT neurons appears to be organized in a very precise manner. It was seen that: 1) The influences on these neurons relaying exteroceptive signals specifically emanated from AGr and Gr areas which in turn received exteroceptive input. 2) The vibrissa units responded to stimulation of foci in either AGr or Gr but the reactivity was greater upon stimulation of Gr than AGr. The incidence of responses was very high when the vibrissa RF was overlapping or adjacent to the region of the cortically-evoked vibrissa movement. The response pattern was mostly excitatory. Responses were rarely observed when vibrissa RF lay distant from the vibrissa moved by cortical stimulation. 3) Neurons with limb RFs responded constantly to stimulation of Gr foci only when the RF was overlapping or adjacent to the region of the cortical motor target; in these two conditions the response pattern was excitatory and inhibitory, respectively. Inhibitions only concerned neurons with forelimb RFs. Responses to stimulation of AGr were rarely obtained. From a functional point of view, the excitatory nature of the cortical control on thalamo-cortical VT neurons suggests that a cortical signal inducing movement of a given body part is able to enhance the afferent transmission of somatosensory messages arising in the same body part. Concerning the control on forelimb neurons, this enhancement would be further amplified by a sort of descending surround inhibition which impairs transmission of messages coming by adjacent body parts.     

Differential expression of calcium-binding proteins in the red nucleus of the developing and adult human brain

The adult human red nucleus consists of two parts: (1) the parvocellular part, which is clearly separated from (2) the magnocellular part. The latter and its rubrospinal projection is known to be rudimentary in the adult human brain. Information concerning the fetal or neonatal features of the red nucleus is sparse. This study is aimed at providing a detailed account of the distribution of three calcium-binding proteins: calretinin (CR), calbindin (CB), and parvalbumin (PV), which are known to be expressed in distinct neuronal populations. Special attention has been paid to transient phenomena. CB was the most abundant protein in the magnocellular part in fetal and perinatal brains; immunoreactive (ir) neurons appeared numerous and densely packed. In the adult only few and widely spaced ir nerve cells were present. CR-expression largely corresponds to that of CB, except that fewer neurons were immunolabelled. In double- labellings the majority of neurons expressed both CB and CR; a moderate number of nerve cells solely expressing CR was present in the magnocellular part. PV-ir fibers and a moderate number of small cells were observed in the fetal, perinatal as well as the adult parvocellular part. A few PV-ir neurons were seen in the magnocellular part of the fetal and perinatal brains. Our results indicated that: (1) the magnocellular and parvocellular parts of the red nucleus were well-demarcated portions from fetal life onwards, thus a dominance of the parvocellular part over the magnocellular occurred during development; (2) the magnocellular part was more prominent in the fetal period than in adulthood; (3) neurons in the red nucleus were heterogeneous with respect to the immunoreactivities towards the three calcium-binding proteins examined; (4) the transient prominence of the magnocellular part might be a substrate for a specific transitory pattern of motor behaviour. Accepted: 7 September 2000     

Immunolocalization of peptide 19 and other calcium-binding proteins in the guinea pig cochlea

Calcium ions are known to play critical roles in a variety of cochlear functions. The distributions of a number of calcium binding proteins that regulate calcium ion levels within the cochlea have previously been described. In this report we extend and refine previous reports of the distribution of immunostaining for calmodulin, calbindin, and calretinin and show for the first time the distribution for peptide 19. There were longitudinal and radial gradients of immunostaining for peptide 19 within outer hair cells that appeared to match previously described gradients of efferent innervation of these cells. Gradients of immunostaining for calbindin within outer hair cells were in the opposite directions, which suggests that levels of this protein are correlated with afferent innervation density and perhaps the abundance of subsurface cisternae. No gradients were seen in the distributions of cells stained for calmodulin and calretinin, which included sensory cells and supporting cells respectively. All ganglion cells were stained for calmodulin but the other proteins appeared to be present in limited ganglion cell subpopulations. In addition to staining of sensorineural elements, antisera to all compounds but peptide 19 showed immunostaining of cells within the lateral wall and the spiral limbus. The results suggest that the proteins under study are involved in a wide variety of calcium-regulated functions within the cochlea. Knowledge of the unique distribution of each of the compounds should facilitate further studies of their roles in cochlear function.     

Changes in retinal neurons in the guinea pig retina stimulated by strobe lights during development

The modern-day population is overexposed to visual stimuli accompanied by contrast and strength changes, such as the television or videogames, beginning early in life. These light stimuli may have an influence on the development of the visual system. The purpose of this study was to examine the effects of light stimuli on retinal development. We reared guinea pigs under a daily 12-h strobe light (2 Hz)/dark cycle from birth, while control animals were reared under a 12-h light/dark cycle. The animals were sacrificed 1, 2, and 4 weeks after birth. The thickness of the outer nuclear layer (ONL) thickness decreased by 14.8% in the strobe-reared animals compared to the control group at 4 weeks, but not at 1 and 2 weeks. The Müller cells of the strobe-reared animals showed a stouter branch compared to that of the control animals at 2 and 4 weeks. In the strobe-reared model, axon-like processes emerging from the rod bipolar cell bodies were observed in the outer plexiform layer (OPL). These findings show that strobe-light stimuli induce morphological changes in retinal neurons, which may lead to the disturbance of normal visual processing during development.     

Distribution of calcium binding proteins in visual and auditory cortices of hamsters

The morphology and distribution of neurons immunoreactive (ir) to parvalbumin (PV), calretinin (CR) and calbindin (CB) were studied in the primary visual (V1) and auditory (A1) cortices of hamsters. Cortical cell populations were labelled immunohistochemically using a glucose oxidase-diaminobenzidine-nickel combined revelation method. Quantitative analysis revealed significant differences between V1 and A1 in the density and distribution of their neuronal population. CBir cells exhibited several typologies in both cortical regions. Most cells were multipolar even though many of them had bitufted or bipolar morphologies. These cells were distributed in layers II/III and in layer V of both A1 and V1, but were more numerous in layer V of V1. CRir cells were of the fusiform type with long bipolar dendritic arbours. These were similarly distributed in both cortices with a peak in superficial layers II/III. PVir cells were also found in both cortices and had round or oval-shaped somata with multipolar processes. They were mostly located in layer V for V1 and in layers III/IV for A1. Visual and auditory primary cortices can thus be differentiated on the basis of their immunoreactivity to specific calcium binding proteins.     

Correlation of the main peripheral branches of the facial nerve with the cytoarchitectonic subdivisions of the facial nucleus in the guinea pig

Summary Correlation of the main peripheral branches of the facial nerve with morphological subdivisions of the facial nucleus was examined in the guinea pig by the retrograde horseradish peroxidase method. The facial nucleus of the guinea pig was divided cytoarchitectonically into the dorsolateral, lateral, intermediate, medio-intermediate, medial, and ventromedial divisions; the ventromedial division was further divided into the major, dorsal and lateral parts. Six main branches of the facial nerve were identified; the zygomatico-orbital, cervical, posterior auricular, anterior auricular, superior labial, and inferior labial branches. After applying HRP to the main branches of the facial nerve, the pattern of distribution of HRP-labelled neuronal cell bodies within the facial nucleus was examined: the dorsolateral division, dorsal part of the ventromedial division, major part of the ventromedial division, lateral part of the ventromedial division, or medial division contained the cell bodies of respectively the zygomatico-orbital, cervical, posterior auricular, anterior auricular, or superior labial branches, while each of the lateral, intermediate, and medio-intermediate divisions contained the cell bodies of both the superior labial and inferior labial branches.     

Immunoreactivity for calcium-binding proteins in the claustrum of the monkey

 The claustrum is topographically and reciprocally connected with many different cortical areas, and anatomical and physiological data suggest it is composed of functionally distinct subdivisions. We asked if the distribution of cells immunoreactive for three calcium-binding proteins, parvalbumin, calbindin D-28k and calretinin would delineate functional subdivisions in the claustrum. We also asked if, as in cortex, different cell types were immunoreactive for the different proteins. We found that cells with parvalbumin-ir were large, multipolar cells. Cells immunoreactive for calretinin were bipolar cells with elongated cell bodies and beaded dendrites. There were three different types of cells immunoreactive for calbindin. The most numerous were small cells with round or oval cell bodies and numerous fine, winding processes. A second type were large multipolar, cells that resembled the parvalbumin-ir cells. The third class were bipolar cells with large, elongated cell bodies. Each type of cell resembles a cell type described in earlier Golgi studies, and each has a morphological cortical counterpart. While the different cell types varied in density, each was seen over the anterior-posterior and dorsal-ventral extent of the claustrum. Accepted: 21 July 1998     

Activity of lateral vestibular nucleus neurons during locomotion in the decerebrate Guinea pig

Summary The influence of locomotor activity upon neurons in the lateral vestibular nucleus was investigated in precollicularly-postmamillary decerebrate guinea pigs. Out of 95 recorded neurons, 24 were identified as vestibulospinal and 71 had no descending projections. Locomotor activity occurred either spontaneously or was prompted by electrical stimulation of the mesencephalic locomotor region. Natural vestibular stimulation was supplied by tilting the animal about its longitudinal axis. Locomotor rhythmic limb muscle activity was accompanied by an increase in the firing frequency in the vast majority of investigated neurons. The increase in frequency was observed at the beginning of ipsilateral forelimb extensor muscle activity. Only in a few non-vestibulospinal neurons was the spontaneous activity depressed during locomotion. An increase in evoked responses was observed in almost all vestibulospinal neurons and in two thirds of the neurons without descending projections. A decrease in evoked responses was observed in one quarter of non-vestibulospinal neurons. During locomotion, the mean and maximal frequencies of evoked neuronal impulse activity changed, but the phase lag of these changes was not altered significantly. The results suggest an enhancement of vestibulospinal influences during locomotion, thus providing a high level of tonus in antigravitational muscles. This is interpreted as a mechanism to ensure that equilibrium is maintained during motion in different gaits and postures.     

Characterization of cochlear nucleus principal cells of Meriones unguiculatus and Monodelphis domestica by use of calcium-binding protein immunolabeling

Antibodies directed against calcium-binding proteins (CaBPs) parvalbumin, calbindin-D28k and calretinin were used as neuronal markers to identify and characterize different principal cell types in the mammalian cochlear nucleus. For this purpose, double immunofluorescence labeling and the combination of CaBP-labeling with pan-neuronal markers were applied to analyze the CaBPs distribution in neurons of the cochlear nucleus (CN) of the Mongolian gerbil (Meriones unguiculatus) and the gray short-tailed opossum (Monodelphis domestica). Despite of the fact, that these two mammalian species are not closely related, principal cell types in the CN of the two species showed many corresponding morphological features and similarities in immunolabeling of the CaBPs. Parvalbumin seems not to be suited as a differential neuronal marker in the CN since it is expressed by almost all neurons. In contrast, calbindin and calretinin were more restricted to specific cell types and showed a mostly complementary labeling pattern. As one of the most interesting findings, calbindin and calretinin were predominantly found in subpopulations of globular bushy cells and octopus cells in the ventral CN. Such a neuron-specific CaBP-expression in subpopulations of morphologically defined cell types argues for a more refined classification of CN cell types in Meriones and Monodelphis. Additionally, other cell types (cartwheel cells, unipolar brush cells, fusiform cells) were marked with calbindin or calretinin as well. Calretinin staining was predominantly observed in auditory nerve fibers and their endings including endbulbs of Held in Meriones. Spherical bushy cells showed a different calretinin-immunolabeling in Meriones and Monodelphis. This species-specific difference may be related to adaptive differences in auditory function.     

Projections to the rostral reticular thalamic nucleus in the rat

Summary Afferent pathways to the rostral reticular thalamic nucleus (Rt) in the rat were studied using anterograde and retrograde lectin tracing techniques, with sensitive immunocytochemical methods. The analysis was carried out to further investigate previously described subregions of the reticular thalamic nucleus, which are related to subdivisions of the dorsal thalamus, in the paraventricular and midline nuclei and three segments of the mediodorsal thalamic nucleus. Cortical inputs to the rostral reticular nucleus were found from lamina VI of cingulate, orbital and infralimbic cortex. These projected with a clear topography to lateral, intermediate and medial reticular nucleus respectively. Thalamic inputs were found from lateral and central segments of the mediodorsal nucleus to the lateral and intermediate rostral reticular nucleus respectively and heavy paraventricular thalamic inputs were found to the medial reticular nucleus. In the basal forebrain, afferents were found from the vertical and horizontal limbs of the diagonal band, substantia innominata, ventral pallidum and medial globus pallidus. Brainstem projections were identified from ventrolateral periaqueductal grey and adjacent sites in the mesencephalic reticular formation, laterodorsal tegmental nucleus, pedunculopontine nucleus, medial pretectum and ventral tegmental area. The results suggest a general similarity in the organisation of some brainstem Rt afferents in rat and cat, but also show previously unsuspected inputs. Furthermore, there appear to be at least two functional subdivisions of rostral Rt which is reflected by their connections with cortex and thalamus. The studies also extend recent findings that the ventral striatum, via inputs from the paraventricular thalamic nucleus, is included in the circuitry of the rostral Rt, providing further evidence that basal ganglia may function in concert with Rt. Evidence is also outlined with regard to the possibility that rostral Rt plays a significant role in visuomotor functions.Abbreviations ac anterior commissure - aca anterior commissure, anterior - Acb accumbens nucleus - AI agranular insular cortex - AM anteromedial thalamic nucleus - AV anteroventral thalamic nucleus - BST bed nucleus of stria terminalis - Cg cingulate cortex - CG central gray - CL centrolateral thalamic nucleus - CM central medial thalamic nucleus - CPu caudate putamen - DR dorsal raphe nucleus - DTg dorsal tegmental nucleus - EP entopeduncular nucleus - f fornix - Fr2 Frontal cortex, area 2 - G gelatinosus thalamic nucleus - GP globus pallidus - Hb habenula - HDB horizontal limb of diagonal band - IAM interanterodorsal thalamic nucleus - ic internal capsule - INC interstitial nucleus of Cajal - IF interfascicular nucleus - IL infralimbic cortex - IP interpeduncular nucleus - LC locus coeruleus - LDTg laterodorsal tegmental nucleus - LH lateral hypothalamus - LHb lateral habenular nucleus - ll lateral lemniscus - LO lateral orbital cortex - LPB lateral parabrachial nucleus - MD mediodorsal thalamic nucleus - MDL mediodorsal thalamic nucleus, lateral segment - Me5 mesencephalic trigeminal nucleus - MHb medial habenular nucleus - mlf medial longitudinal fasciculus - MnR median raphe nucleus - MO medial orbital cortex - mt mammillothalamic tract - OPT olivary pretectal nucleus - pc posterior commissure - PC paracentral thalamic nucleus - PF parafascicular thalamic nucleus - PPTg pedunculopontine tegmental nucleus - PrC precommissural nucleus - PT paratenial thalamic nucleus - PV paraventricular thalamic nucleus - PVA paraventricular thalamic nucleus, anterior - R red nucleus - Re reuniens thalamic nucleus - RRF retrorubral field - Rt reticular thalamic nucleus - Scp superior cerebellar peduncle - SI substantia innominata - sm stria medullaris - SNR substantia nigra, reticular - st stria terminalis - TT tenia tecta - VL ventrolateral thalamic nucleus - VO ventral orbital cortex - VP ventral pallidum - VPL ventral posterolateral thalamic nucleus - VTA ventral tegmental area - 3 oculomotor nucleus - 3V 3rd ventricle - 4 trochlear nucleus     

Ontogeny of two calcium-binding proteins (calbindin D-28K and parvalbumin) in the human inferior olivary complex and their distribution in the adults

The inferior olivary complex (IOC) is a prominent nuclear relay system of the medulla oblongata. Anatomically, it is connected to the cerebellum for coordination of motor activities. Calbindin D-28K (CALB) and parvalbumin (PV) are cytosolic calcium-binding proteins (CBP) that play a role in Ca²⁺ homeostasis. We examined their ontogeny and distribution in the fetal, postnatal and adult human IOC by immunohistochemistry. At 11–12 weeks of gestation (wg), calbindin immunoreactivity was present in the principal olive and the medial accessory olive, it was absent in the dorsal olive. Parvalbumin immunoreactivity developed at 16–17 wg in the ventral lamella and the lateral bulge of the principal olive only. Calbindin expression gradually increased from 20 to 37 wg, whilst by contrast, parvalbumin expression was moderate. By 37 wg, all three IOC subnuclei were immunopositive for both proteins. In a 3-month-old infant, parvalbumin was intensely developed in the olivary axons. In the adults (40- to 59-year-old), calbindin was distributed in most neurons, and olivocerebellar fibres, whereas parvalbumin was present in some neurons and few fibres. Parvalbumin expressed till 51 years, and disappeared by 59 years of age. Calbindin immunoreactivity in the olivary axons was declined at 70 years of age. The data suggest a differential distribution and requirement of these proteins in the human IOC maturation. It may be that the IOC utilizes mainly calbindin for Ca²⁺ buffering. The loss of parvalbumin with ageing might influence the excitability of the spared IOC neurons.     

Calcium-binding Proteins in Avian Herbst and Grandry sensory corpuscles

Background: Calcium-binding proteins (Ca²⁺-BP) are involved in the homeostasis of intracellular calcium ions (Ca²⁺), which play a key role in electrogenesis, and therefore in somatosensory transduction, within sensory corpuscles. This study analyze the distribution of several Ca²⁺-BP in avian Herbst and Grandry sensory corpuscles. Methods: Specimens of beak skin and tongue from ducks and pigeons were studied immunohistochemically using antibodies against S100 protein (S100P), calretinin (CR), calbindin D^28K (CB), and parvalbumin (PV). Moreover, neurofilament proteins (NFP) and neuron-specific enolase (NSE) were studied in parallel. Results: In Herbst corpuscles: (1) specific immunoreactivity (IR) for S100P was always observed labelling the inner-core cells and was also found in the capsule of duck Herbst corpuscles; (2) all the other investigated Ca²⁺-BP were found primarily in the inner-core, without relevant species-specific differences, but also in the central axon and in the capsule (CB and PV). In Grandry corpuscles, the Grandry cells (1) can be subdivided on the basis of S100P IR; (2) displayed a strong CR IR, moderate PV IR, and weak CB IR; (3) were negative for NFP or NSE. On the other hand, the central axon of both kinds of sensory corpuscles showed NFP and NSE IR, and the intraepidermic Merkel-like cells were NFP IR. Conclusions: Present results provide evidence for the presence of several Ca²⁺-BP in two kinds of rapidly adapting avian sensory corpuscles, and also for the existence of species-specific differences in the localization of some of them. These findings suggest that Ca²⁺-BP may be involved in the maintenance of Ca²⁺ homeostasis in avian sensory corpuscles, and therefore in mechano-electric transduction. © 1995 Wiley-Liss, Inc.     

Modulation of Ca current during the phosphorylation cycle in the guinea pig heart

The calcium current (I _Ca) in the heart is increased by phosphorylation of a protein which is part of, or close to, the Ca channel. The phosphorylation is catalysed by cAMP-dependent protein kinase (cAMP-PK). The question whether dephosphorylated channels are available to open on depolarization was examined in ventricular myocytes of guinea pig by recording whole cellI _Ca during dialysis with either regulatory (R) subunit of cAMP-PK or protein kinase inhibitor (PKI) or adenosine-5-(-thio)-triphosphate (ATPS). The following results were obtained: 1) R subunit reduced and PKI reversed the isoprenaline (ISP)-induced enhancement ofI _Ca, suggesting their ability to inhibit cAMP-PK. 2) R subunit and PKI, however, reduced basal (i.e. non -adrenergically stimulated)I _Ca only by about 20%. 3) Dialysis with ATPS resulted in a slow increase in basalI _Ca, presumably due to dephosphorylation-resistant thiophosphorylation. 4) When, however, the cell was dialyzed with PKI the effect of ATPS was almost completely suppressed, suggesting no detectable phosphorylation related to the channel activity in this condition. These results support the view that even in the dephosphorylated state Ca channels are available to open on depolarization and that phosphorylation by cAMP-PK increases the opening probability.This work was supported by the Deutsche Forschungsgemeinschaft, SFB 38 (Membranforschung), Projekt G, and HO 579/6-2     

Immunoreactivity for calcium-binding proteins defines subregions of the vestibular nuclear complex of the cat

The vestibular nuclear complex (VNC) is classically divided into four nuclei on the basis of cytoarchitectonics. However, anatomical data on the distribution of afferents to the VNC and the distribution of cells of origin of different efferent pathways suggest a more complex internal organization. Immunoreactivity for calcium-binding proteins has proven useful in many areas of the brain for revealing structure not visible with cell, fiber or Golgi stains. We have looked at the VNC of the cat using immunoreactivity for the calcium-binding proteins calbindin, calretinin and parvalbumin. Immunoreactivity for calretinin revealed a small, intensely stained region of cell bodies and processes just beneath the fourth ventricle in the medial vestibular nucleus. A presumably homologous region has been described in rodents. The calretinin-immunoreactive cells in this region were also immunoreactive for choline acetyltransferase. Evidence from other studies suggests that the calretinin region contributes to pathways involved in eye movement modulation but not generation. There were focal dense regions of fibers immunoreactive to calbindin in the medial and inferior nuclei, with an especially dense region of label at the border of the medial nucleus and the nucleus prepositus hypoglossi. There is anatomical evidence that suggests that the likely source of these calbindin-immunoreactive fibers is the flocculus of the cerebellum. The distribution of calbindin-immunoreactive fibers in the lateral and superior nuclei was much more uniform. Immunoreactivity to parvalbumin was widespread in fibers distributed throughout the VNC. The results suggest that neurochemical techniques may help to reveal the internal complexity in VNC organization.     

Direct projections of the hypothalamic nuclei to the thalamic mediodorsal nucleus in the cat

Direct projections of the hypothalamic nuclei to the thalamic mediodorsal nucleus (MD) were studied using retrograde and anterograde transport of horseradish peroxidase (HRP) and wheat germ agglutinin (WGA)-HRP. HRP and WGA-HRP were injected into the MD, thalamic paraventricular, lateral habenular and hypothalamic nuclei. The results indicate that the MD, particularly its medial part, receives a moderate amount of hypothalamic afferents, and that most of these afferents originate in the medial part of the lateral hypothalamic nucleus at anterior levels, while a limited number are derived from the dorsal, dorsomedial, ventromedial and anterior hypothalamic and lateral preoptic nuclei.