Immunohistochemical mapping of calcium-binding protein immunoreactivity in the rat central nervous system

Immunocytochemical characterization of neuron-rich rat brain primary cultures: calbindin D28K as marker of a neuronal subpopulation

The function in neurons of the vitamin D-dependent calcium ion-binding-protein of 28 kDa mol. wt., calbindin D28K, is unknown. In order to find a simple system for studying the function of this protein, neuron-rich primary cultures derived from brains of 16-day-old rat embryos were analyzed for the presence of calbindin D28K by immunocytochemical mono- and double-labelling techniques. The studies were carried out between the 5th and 23rd day after seeding. In contrast to the neuronal marker neuron-specific enolase which was found in nearly all cells in the culture, calbindin D28K was expressed only in a subpopulation of neurons. Calbindin D28K-positive cells were intensely stained in their cell bodies and were also stained in their processes. Astroglial cells identified by the presence of the processes. Astroglial cells identified by the presence of the specific marker glial fibrillary acidic protein did not express calbindin D28K. Therefore, calbindin D28K is a useful marker for defining a neuronal subpopulation in neuron-rich primary cultures. Such cultures may be employed as a tool in searching for function(s) of calbindin D28K.

Two calcium-binding proteins mark many chick sensory neurons

The first immunohistochemical results with a new neuronal calcium-binding protein, calretinin, are presented. Calretinin is related to the 28,000 mol. wt calcium-binding protein, calbindin, and a survey of the chick brain by in situ hybridization has identified the brain nuclei that expressed the genes for the two proteins [Rogers J.H., J. Cell Biol. 105, 1343 (1987)]. Now, antisera have been raised against calretinin fusion proteins in order to visualize individual neurons. The antisera have been used in an immunohistochemical survey of calretinin and calbindin in the chick sensory nuclei and ganglia, where these two proteins are found to be particularly prevalent. In the central nervous system, they are seen in many secondary sensory neurons and local circuit neurons, the two proteins being almost always in separate cells. However, in ganglion cells of the spinal nerves, inner ear, and retina, they are often expressed together. Their distribution in the brain is generally different from that of a third calcium-binding protein, parvalbumin. These proteins may modulate many important calcium-dependent processes in neurons, and probably have multiple functions.

Tissue-specific regulation of the concentration of calbindin D28K mRNA in the developing chicken

A BamHI-HindIII restriction fragment containing the 5'-terminal portion of the gene encoding chicken Calbindin D28K was sequenced and used as a probe in Northern-blot hybridizations to RNA extracted from the brain and intestine of chickens at various stages of development. In both tissues Calbindin D28K mRNA consists of a family of three species, which differ by size. In the intestine Calbindin D28K mRNAs appear at hatching and reach a peak at day 7. In the brain the same RNA species are easily detected at least 7 days before hatching, show a moderate increase at hatching and remain essentially constant during the first 10 days of adult life. The concentration of Calbindin D28K mRNAs in the intestine is strictly dependent on Vitamin D, while it is not in the cerebellum.

Calbindin-D28 in mammalian brain, retina, and endocrine pancreas: immunohistochemical comparison with calretinin

Calbindin 28K and calretinin are very similar calcium binding proteins which are both present in the central nervous system (CNS). They respectively bind 4 and 5 Ca++ ions. We have compared by immunohistochemistry and in situ hybridization their localisation in the brain and the retina. The two proteins are generally expressed in different neurons with a few neurons containing both calcium binding proteins. Calbindin 28K is also present in the endocrine system. We have examined the cellular distribution of calbindin in the pancreatic endocrine cells of chick, rat and human and found variable distribution among the different endocrine cell types. We also describe the presence of calbindin in RINm5F cells, an insulin-producing tumor cell line derived from a radiation-induced rat insulinoma.

Analysis of parvalbumin and calbindin D28k-immunoreactive neurons in dorsal root ganglia of rat in relation to their cytochrome oxidase and carbonic anhydrase content

Histochemical and immunohistochemical techniques were used to determine relationships between the parvalbumin or calbindin D28k content and the cytochrome oxidase or carbonic anhydrase activity of neurons in lumbar dorsal root ganglia in rat. Subpopulations of dorsal root ganglion neurons that displayed parvalbumin- or calbindin D28k-immunoreactivity were classified as containing either light, moderate or dense histochemical reaction product for cytochrome oxidase and either a positive or negative reaction for carbonic anhydrase. It was found that approximately 90% of all parvalbumin and calbindin D28k-immunoreactive cells exhibited dense staining for cytochrome oxidase and that 87% of parvalbumin- and 76% of calbindin D28k-immunoreactive cells were positive for carbonic anhydrase. Conversely, 85% of all cells with a dense cytochrome oxidase reaction contained parvalbumin and calbindin D28k. Although not quantified, it appeared that many, but not all, carbonic anhydrase-positive cells contained parvalbumin or calbindin D28k. These results indicate the existence of a subpopulation of primary sensory neurons that contains parvalbumin and calbindin D28k and that expresses high levels of cytochrome oxidase and carbonic anhydrase activity. It is suggested that primary afferent neurons with this cytochemical profile transmit a sensory modality that requires them to discharge rapidly and/or frequently. The existence of a subpopulation of carbonic anhydrase-positive cells that lack immunoreactivity for parvalbumin or calbindin D28k suggests that the role of carbonic anhydrase in some sensory neurons is unrelated to functions requiring these calcium binding proteins.

On the molecular mechanism of intestinal calcium transport

The intestinal absorption of calcium is certainly a complex process, dependent on several factors of which vitamin D, via 1,25(OH)2D3, is the major controlling hormone. The efficiency of calcium absorption is a function of calcium status and calcium need. As the body's demand for calcium increases, the process commonly termed, adaptation, is activated in which the synthesis of 1,25(OH)2D3 from precursor is increased, resulting in the stimulation of the rate of calcium absorption. The increased demand for calcium might result from the ingestion of a diet deficient in calcium, from growth, pregnancy, lactation and egg shell formation in the laying hen. Accomapanying the change in calcium absorptive efficiency are molecular modifications of the transporting enterocytes, some mentioned herein and elsewhere (Wasserman & Chandler, 1985; Wasserman, 1980; Wasserman et al., 1984). Highly correlated with the rate of calcium absorption under a wide variety of conditions is the concentration of the vitamin D-induced calcium-binding protein, calbindin-D28K (avian type) and calbindin-D9K (mammalian intestinal type). The role of calbindin-D in this transport process is not precisely known but is considered to act at the present time as a cytosolic facilitator of Ca2+ diffusion from the brush border membrane to the basolateral membrane. In addition to the induction of calbindin-D synthesis, 1,25(OH)2D3 exerts other effects on the intestinal epithelium that can have consequences on the calcium absorptive process. Some of these effects are summarized in Figure 14. Vitamin D-dependent reactions might be either direct effects of 1,25(OH)2D3 or indirect effects due to elevated intracellular Ca2+ concentrations. These include changes in the fluidity of the brush border membrane, an increase in microvillar alkaline phosphatase-low affinity Ca-activated ATPase activity, an association of calmodulin with the 105 kD brush border cytoskeletal protein and, following calbindin D synthesis, the binding of calbindin D to a 60 kD brush border protein and to microtubules. The latter has been suggested to be related to the proposed transfer of Ca2+ by an endocytotic-exocytotic mechanism. In addition, a vitamin D-dependent intestinal membrane calcium-binding protein has been identified (Kowarski & Schachter, 1980). Playing into this multi-component system is a stimulation of cyclic nucleotide synthesis by 1,25(OH)2D3 which, through activation of cyclic nucleotide-dependent protein kinases, might modify membrane Ca2+ "channels" by phosphorylation reactions.4+ Intracellular organelles, i.e., the endoplasmic reticulum, mitochondria, the Golgi apparatus, are potent sequesters of Ca2+ and could contribute to the protection of the cell from excessively high Ca2+ concentrations by transiently storing absorbed Ca2+.

Calcium currents in rat cerebellar Purkinje cells maintained in culture

Calcium permeabilities were examined in large cerebellar neurons maintained in culture, and morphologically identified as Purkinje cells. When cells were supplied with a Dulbecco Minimum Eagle's Medium with 10% horse serum added (5-10 days), somatic recordings revealed complex spikes and these were shown to be generated by Na and Ca components, the Na one being tetrodotoxin-sensitive. At the dendritic level, Ca currents were better resolved than at the soma. In dendrites, Ca entry was shown to occur through at least two distinct currents. The first was a low-threshold transient current (elicited above -60 mV from a holding potential of -80 mV) which was reduced by almost 30% by 50 microM cadmium. The second was a high-threshold current (above -20 mV) which gave rise to (1) a transient component exhibiting a steady-state inactivation and so requiring holding potentials at -80 mV, and (2) a sustained component. Both components were suppressed by 50 microns cadmium. We measured a total Ca current at the dendritic level reaching values of up to 1 nA. In another culture medium (Leibovitz medium) known to allow expression of three types of calcium currents in nodose cells we observed the development of the dendritic tree of Purkinje cells but with no simultaneous expression of the high-threshold Ca current.

Immunoreactivity for calretinin and other calcium-binding proteins in cerebellum

Two calcium-binding proteins, calbindin and parvalbumin, have been reported to be abundant in Purkinje cells and other cell types in the cerebellum. Immunoreactivity for a related protein, calretinin, is now reported in cerebellum of chick and rat. In the chick, antibodies against calretinin stain mossy fibres throughout, and climbing fibres in a distinct group of folia. They also stain several cell types in the molecular layer. As there is no detectable calretinin mRNA in the cerebellar cortex, this cellular staining may be due to cross-reaction with an unknown antigen. In the rat, antibodies against calretinin stain the Lugaro cells, and some granule cells in lobe X; they also give weak staining of all the granule cells in the other lobes. Thus almost all the neuronal cell types in the cerebellum show immunoreactivity for at least one of the calcium-binding proteins in one or both species.

Postnatal development of parvalbumin-, calbindin- and adult GABA-immunoreactivity in two visual nuclei of zebra finches

The characterization of neuron populations by their immunoreactivity against parvalbumin- and calbindin (28-kDa)-antisera has been used to study the postnatal development of the visual diencephalic nucleus rotundus and the mesencephalic nucleus isthmi complex in zebra finches. In nucleus rotundus, parvalbumin-immunoreactivity was restricted to the neuropil during the first 10 days and appears additionally in somata around day 12 where it remains until adulthood. Calbindin-immunoreactivity of the very scarce neuropil and the few somata, which can be observed during the first two weeks, disappears until adulthood. Thus, the adult nucleus rotundus shows an almost complementary distribution of calbindin- and parvalbumin-immunoreactive structures: the numerous, heavily parvalbumin-positive somata, which are surrounded by dense immunoreactive neuropil are in sharp contrast to the complete absence of calbindin-immunoreactive somata. Only a thin rim surrounding this nucleus contains punctate calbindin-positive neuropil. In the nucleus isthmi complex, parvalbumin and calbindin staining patterns show markedly different developmental profiles. While the density of parvalbumin-immunoreactive neuropil in the parvocellular part of the nucleus isthmi continuously increases and the somata remain unstained, the initially heavily calbindin-positive somata gradually lose their immunoreactivity during the first two weeks. In the adult nucleus isthmi complex, parvalbumin- and calbindin show nearly identical staining patterns. A comparison between the two calcium-binding proteins and GABA-immunoreactivity in adult brains revealed different relationships in the two nuclei: while in nucleus rotundus GABA-staining pattern neither resembles that of parvalbumin nor of calbindin, in the nucleus isthmi complex all three staining patterns coincide.

Regulation of brain and cerebrospinal fluid calcium by brain barrier membranes following vitamin D-related chronic hypo- and hypercalcemia in rats

Male Fischer-344 rats, 21 days old, were fed diets containing 0 (LOD), 2,200 (CONT), or 440,000 (HID) international units of vitamin D3 per kilogram for 12 weeks. [Ca] was measured in plasma, CSF, brain, and choroid plexus. In addition, 45Ca and 36Cl transfer coefficients (KCa and KCl) for uptake from blood into CSF and brain were determined. Although plasma ionized [Ca]s in LOD and HID rats were 50% and 136%, respectively, of values in CONT animals, CSF and brain [Ca]s ranged from only 85% to 110% of respective CONT values. Choroid plexus [Ca] was increased by 37% after HID diet, but was decreased only 10% after LOD. KCa values at CSF, parietal cortex, and pons-medulla were negatively correlated with plasma ionized [Ca], whereas KCl values at CSF and brain were not different between the diet groups. The findings demonstrate that central nervous system [Ca] is maintained during chronic hypo- or hypercalcemia by saturable transport of Ca at brain barrier membranes. This transport does not seem to involve modulation by 1,25-dihydroxyvitamin D3.

Molecular cloning of mammalian 28,000 Mr vitamin D-dependent calcium binding protein (calbindin-D28K): expression of calbindin-D28K RNAs in rodent brain and kidney

We report the isolation of a cloned cDNA for the mammalian 28,000 Mr vitamin D-dependent calcium binding protein (calbindin-D28K; CaBP28K) by immunological screening of a lambda gt11 bacterial expression library. The library contained cDNAs copied from poly(A)RNA of adult mouse cerebellum. We confirmed the identity of the CaBP28K cDNA by comparing its DNA sequence with that of chick CaBP28K cDNA. In the coding region, 79% of the mouse cDNA sequence was identical to the reported sequence of CaBP28K cDNA derived from chicken intestine. Rat brain and kidney each contain three species of poly(A)RNA that hybridize to CaBP28K cDNA--a major species of 1.9 kb, and rarer components of 2.8 kb and 3.2 kb. All three RNAs appear to be transcribed from a single gene. The ratios of these CaBP28K RNAs were the same in brain and kidney. In the cerebellum, in situ hybridization reveals that CaBP28K RNAs are confined to Purkinje neurons.

Localization of calbindin D28 mRNA in rat tissues by in situ hybridization

We investigated, by in situ hybridization histochemistry, the cellular localization of the mRNA encoding a vitamin D-dependent calcium-binding protein (calbindin D28) in rat brain and peripheral organs. Using a [35S]cRNA probe under high stringency conditions, specific mRNA was found in tissues well known for their calbindin D28 content, e.g. renal distal tubules, cerebellar Purkinje cells and dentate gyrus granule cells. Tissue devoid of this protein, such as liver, also lacked specific mRNA. In situ hybridization histochemistry allows the precise identification of cells expressing calbindin D28 and offers a new approach to study its regulation and possible role, e.g. in neuronal function.

Distribution and co-localization of calbindin D28k with VIP and neuropeptide Y but not somatostatin, galanin and substance P in the enteric nervous system of the rat

Calbindin D28k, previously demonstrated in the mammalian central nervous system, has been localized to discrete neurons in the enteric nervous system of the rat. Calbindin D28k is present in cell bodies in both the myenteric and submucous plexi and in interganglionic nerve fibers in all regions of the gastrointestinal tract. Immunoreactive nerve fibers were also detected in the mucosal region, although none were observed in the pyloric sphincter, circular or longitudinal muscle layers. The highest concentration of immunoreactivity was present in the submucosal plexus and mucosa of the colon. Western blot analysis of the protein detected by the antiserum confirmed that it comigrated with purified calbindin D28k and the single immunoreactive band seen in extracts from rat brain. The colocalization of calbindin D28k with components of the peptidergic innervation was also investigated. Of the peptides studied the neurons containing both vasoactive intestinal polypeptide and neuropeptide Y in the submucous plexus were seen to exhibit calbindin D28k immunoreactivity. The neurons containing somatostatin, galanin and substance P did not demonstrate co-localization. In the stomach, calbindin D28k was detected within a small number of epithelial cells which were found to correspond to a sub-population of the somatostatin-immunoreactive endocrine cells.

1,25(OH)2 vitamin D3 sites of action in spinal cord and sensory ganglion

Autoradiographic studies revealed concentration of 3H 1,25(OH)2 vitamin D3 in nuclei of certain neurons in the spinal cord of adult and neonatal mice, fed a normal or a vitamin D deficient diet. Nuclear uptake and retention was strongest in motor neurons in lamina IX. Nuclear concentration also existed in neurons of lamina II, lamina VIII, lamina X and intermediate nucleus of the lateral column. The results indicate that these neurons are target neurons which contain nuclear receptors for 1,25(OH)2 vitamin D3. This suggests that 1,25(OH)2 vitamin D3 has direct genomic actions on the innervation of skeletal muscle by exerting related trophic, secretory, and electrophysiological effects. In addition, these data point to direct genomic actions of 1,25(OH)2 vitamin D3 on spinal sensory perception, and on certain autonomic functions. Nuclear binding in certain neurons in the peripheral ganglion of the trigeminal nerve further suggests that sensory perception is influenced by 1,25(OH)2 vitamin D3 not only at the level of the substantia gelatinosa, but also at the level of spinal ganglia.

Comparison of calbindin D-28K immunoreactivity in superficial pineal bodies of mongolian gerbil and rat

Immunocytochemical reaction for demonstration of calbindin D-28K has been performed in superficial pineal bodies of the Mongolian gerbil (Meriones unguiculatus) and the rat. Whereas in the Mongolian gerbil there were no clearly expressed calbindin immunoreactive cells, these were numerous in the rat pineal body. Here the calbindin-positive cells - probably pinealocytes - were disposed along capillaries. In view of the role of calbindin in binding and transporting calcium and regulating its intracellular levels, the absence of this protein in the gerbil pineal body has been interpreted as signifying the inability of pinealocytes to eliminate intracellular calcium with possible consequent formation of acervuli.

Ontogeny of the calcium binding protein calbindin D-28k in the rat nervous system

Calbindin D-28k immunoreactivity appeared at embryonal day 14 (E14) in the central nervous system as well as in the sensory organs and at E15 in the peripheral nervous system of the rat. At E14 the infundibular process of the diencephalon, cells of the posterior hypothalamus and of the dorsal thalamus were the only structures strongly immunostained in the brain, whereas neurons of the basal plate of the spinal cord, medulla oblongata and of the outermost layer of the cerebral cortex were only faintly labeled. Calbindin positive cerebellar Purkinje cells could be discerned at E15 together with a few cells in the hippocampus and in ganglia of the cranial nerves. At E19 various mesencephalic and metencephalic structures, spinal ganglion cells and basal ganglia displayed calbindin immunoreactive cells. The adult pattern of calbindin immunoreactivity (Garcia Segura et al. 1984) was reached before birth in most brain regions. In general, cells which displayed calbindin during brain development were also calbindin positive in the adult animal. Exceptions to this rule were cells of deep nuclei of the cerebellum and non-neuronal cells which transiently expressed calbindin during development. Calbindin appeared in a given brain region almost invariably 1 or 2 days after the cessation of cell division and the beginning of neuronal migration and extension of neuronal processes. The calcium binding protein calbindin might influence these Ca2+-dependent processes.

Calbindin-D in peripheral nerve cells is vitamin D and calcium dependent

The vitamin D-induced calcium-binding protein calbindin-D (CaBP) was localized immunohistochemically in some but not all of the cell bodies and axons within the intestinalis nerve of the chicken. Unlike other nerve tissue thus far examined, the CaBP content of the intestinalis nerve was decreased in vitamin D deficiency and increased in chicken adapted to a calcium-deficient diet. These changes are qualitatively similar to the pattern of response of enterocytes. The inclusion of calcium-containing solutions within the duodenal lumen caused, directly or indirectly, a decrease in the amount of CaBP in this nerve in a dose-dependent manner. The exact role of CaBP in intestinalis nerve cells is unknown but may be in the regulation of intracellular ionic Ca2+ concentrations during excitation, although other functions of CaBP cannot be excluded.

Calretinin: a gene for a novel calcium-binding protein expressed principally in neurons

A novel gene of the calmodulin superfamily, encoding a 29-kD neuronal protein here named "calretinin," has been isolated as a cDNA clone from chick retina. The encoded sequence includes four putative calcium-binding sites and a fusion protein binds calcium. The most similar protein known is the 28-kD intestinal calcium-binding protein, calbindin (58% homology). Both genes date from before the divergence of chicks from mammals. The distribution of calretinin and calbindin mRNAs in chick tissues has been mapped using RNA gel blots and in situ hybridization. RNAs from both genes are abundant in the retina and in many areas of the brain, but calretinin RNA is absent from intestine and other nonneural tissues. Calretinin and calbindin are expressed in different sets of neurons throughout the brain. Calretinin RNA is particularly abundant in auditory neurons with precisely timed discharges.

Immunohistochemical localization of calcium-binding proteins, parvalbumin and calbindin-D 28k, in the adult and developing visual cortex of cats: a light and electron microscopic study

In the cat primary visual cortex, we investigated with immunohistochemical techniques the developmental changes in the cellular and subcellular localization of the Ca2+-binding proteins parvalbumin (PV) and calbindin-D 28K (CBP), in order to determine whether there is a correlation between the expression of Ca2+-dependent processes and the time course of the critical period for use-dependent plasticity. On the 54th day of gestation and at 1 week postnatally, both calcium-binding proteins were present only in a subpopulation of neurons in layers V and VI. During subsequent maturation, the number of PV(+) and CBP(+) neurons increased significantly and labeled cells were detected in more superficial layers. Moreover, the homogeneous labeling of some CBP(+) neurons in layers IV to VI decreased and changed to a punctate pattern. In adult cats PV(+) neurons were evenly distributed throughout layers II to VI, whereas CBP(+) neurons were concentrated in layers II/III. Only a few immunoreactive cells had morphological features characteristic of pyramidal cells; the large majority were nonpyramidal. Electron microscopy confirmed the presence of PV- and CBP-reaction product within the perikarya, axons, and dendrites of labeled cells. It was associated preferentially with microtubules, postsynaptic densities, and intracellular membranes. Immunoreactive neurons received immunonegative asymmetric synapses on their dendritic shafts and made symmetric synaptic contacts with labeled and unlabeled somata and with unlabeled dendritic shafts. The large number and widespread distribution of immunoreactive neurons implies that PV and CBP play an important role in the regulation of calcium-dependent processes in the visual cortex. Furthermore, the developmental redistribution of PV and CBP points to changes in the organization of Ca2+-dependent processes during maturation.

Developmental and functional studies of parvalbumin and calbindin D28K in hypothalamic neurons grown in serum-free medium

The Ca2+-binding proteins parvalbumin (Mr = 12K) and calbindin D28K [previously designated vitamin D-dependent Ca2+-binding protein (Mr = 28K)] are neuronal markers, but their functional roles in mammalian brain are unknown. The expression of these two proteins was studied by immunocytochemical methods in serum-free cultures of hypothalamic cells from 16-day-old fetal mice. Parvalbumin is first detected in all immature neurons, but during differentiation, the number of parvalbumin-immunoreactive neurons greatly declines to a level reminiscent of that observed in vivo, where only a subpopulation of neurons stains for parvalbumin. In contrast, calbindin D28K was expressed throughout the period investigated only in a distinct subpopulation of neurons. Depolarization of fully differentiated hypothalamic neurons in culture resulted in a dramatic decrease of parvalbumin immunoreactivity but not of calbindin D28K immunoreactivity. The parvalbumin staining was restored on repolarization. Because the anti-parvalbumin serum seems to recognize only the metal-bound form of parvalbumin, the loss of immunoreactivity may signal a release of Ca2+ from intracellular parvalbumin during depolarization of the cells. We suggest that parvalbumin might be involved in Ca2+-dependent processes associated with neurotransmitter release.

Calbindin in vertebrate classes: immunohistochemical localization and Western blot analysis

Calbindin immunoreactivity was investigated in various vertebrates. Positive labeling was observed in the absorptive cells of the duodenum of all birds and reptiles but not in mammals, amphibia, or fish. Staining was present in the kidney distal convoluted tubule from amphibia and higher vertebrates. Fish kidney was negative. In the central nervous system of all species investigated, cellular bodies and fibers were Calbindin positive. Their distribution was quite broad and correlates well with the previously reported mapping for chick and rat. Western blot analysis revealed two Calbindins in brain from mammals, birds, reptiles, and amphibia (27,000 and 29,000 Da). Only one band was detected in fish. We conclude that Calbindin from the evolutionary point of view is primarily a neuronal protein, with a highly conservative character.

1,25 (OH)2 vitamin D3 sites of action in the brain. An autoradiographic study

After injection of 3H 1,25 (OH)2 vitamin D3 to adult rats and mice, under normal or vitamin D deficient diet, the hormone was found to be accumulated in nuclei of neurons in certain brain regions. Nuclear concentration was prevented or diminished, when excess unlabeled 1,25 (OH)2 vitamin D3 was injected before 3H 1,25 (OH)2 vitamin D3, while excess 25 (OH) vitamin D3 did not prevent nuclear labeling. Highest nuclear concentration of 3H 1,25 (OH)2 vitamin D3 is observed in certain neurons in the nucleus interstitialis striae terminalis, involving its septo-preoptic pars dorsolateralis and its anterior hypothalamic-thalamic portion, and in the nucleus centralis of the amygdala, all constituting a system of target neurons linked by a component of the stria terminalis. Nuclear concentration of 3H 1,25 (OH)2 vitamin D3 is also found in neurons in the periventricular nucleus of the preoptic-hypothalamic region, including its extensions, the parvocellular paraventricular and arcuate nucleus, in the ventromedial nucleus, supramammillary nucleus, reticular nucleus of the thalamus, ventral hippocampus, caudate nucleus, pallium, in the midbrain-pontine central gray, dorsal raphe nucleus, parabrachial nuclei, cranial motor nuclei, substantia gelatinosa of the sensory nucleus of the trigeminus, Golgi type II cells of the cerebellum, and others. The extensive distribution of target neurons suggests that 1,25 (OH)2 vitamin D3 regulates the production of several aminergic and peptidergic messengers, and influences the activity of certain endocrine-autonomic, sensory and motor systems.

Selective localization of calcium-binding protein in human brainstem, cerebellum and spinal cord

The 28,000-Da vitamin D-dependent calcium-binding protein, CaBP, which is induced by one hormonally active form of vitamin D3, 1,25-dihydroxyvitamin D3, was localized by immunocytochemistry in the human brainstem, cerebellum and cervical segment of the spinal cord. Positive structures (neurons and their processes) were restricted to some well-defined motor and sensory pathways. In motor regions, the highest density of immunoreactive sites was found in the Purkinje cell layer of the cerebellar cortex, and CaBP-positive neurons were also found in the reticular formation and the inferior olivary nucleus. In sensory pathways, positive neurons were mainly localized in structures associated with protopathic thermalgesia (pain and temperature), as well as in the solitary nucleus and parabrachial nucleus of the taste pathway.

Calbindin immunoreactivity alternates with cytochrome c-oxidase-rich zones in some layers of the primate visual cortex

Calcium ions have a pivotal role in many neuronal activities, but little is known about their involvement in the cortical processing of visual information. Using immunohistochemical methods, we have now detected a calcium-binding protein, calbindin-D-28K, which may confer on certain compartments of cortical area 17 the ability to modulate Ca2+ metabolism. Thus, calbindin occurs in the primate striate cortex in a pattern almost complementary to that displaying strong cytochrome c-oxidase activity. From this and other observations, we deduce that the distribution of calbindin-immunoreactive sites corresponds mainly to extra-geniculocortical connections of the primary visual cortex. This implies that the geniculocortical and extra-geniculocortical compartments of area 17 differ in an intracellular system for Ca2+ homeostasis.

Parvalbumin in rat kidney. Purification and localization

The Ca2+-binding parvalbumin has been purified for the first time from rat kidney. Its biochemical and immunological properties were indistinguishable from the muscle counterpart. By immunohistochemical methods parvalbumin was localized in part of the distal tubule and proximal collecting duct, similar to the vitamin D-dependent Ca2+-binding protein, calbindin-28K. Parvalbumin was found to be independent of the vitamin D status of the animal since its concentration remained unchanged in kidney extracts of normal, rachitic and vitamin D-replete rats. Both proteins may be involved in the regulation of intracellular Ca2+ in kidney.

Nucleus basalis Meynert neurons contain the vitamin D-induced calcium-binding protein (Calbindin-D 28k)

The neurons of the monkey basal nucleus of Meynert are shown to contain a protein indistinguishable from the chicken intestinal 28kd vitamin D-dependent calcium-binding protein (Calbindin-D 28k; CPB). CBP is thought to shuttle and buffer Ca++-ions, thus regulating the intracellular calcium distribution and concentration. Our observation may engender interest in searching for the role Vitamin D-metabolites, the CBP and calcium-ions in the physiology and pathology of nucleus basalis Meynert neurons.

Tyrosine hydroxylase and 28K-vitamin D-dependent calcium binding protein are localized in different subpopulations of periglomerular cells of the rat olfactory bulb

Successive incubations of rat olfactory bulb cryostat sections with antibodies against the chick 28K-vitamin D-dependent calcium (Ca) binding protein and tyrosine hydroxylase were performed, and the distribution of the label was examined in the fluorescence microscope. Both antibodies labeled cells and processes in highest number in the glomerular layer. The two immunopositivities were not co-localized in the same neurons. This suggests that the presence of this Ca-binding protein is not a necessary prerequisite for dopaminergic neurotransmission in periglomerular neurons.

Reduction of rat hippocampal calcium-binding protein following commissural, amygdala, septal, perforant path, and olfactory bulb kindling

The calcium-binding protein (CaBP) content of the hippocampal formation was determined by radioimmunoassay in control and kindled rats. Kindling of a number of different sites resulted in a reduction in the CaBP content of the hippocampal formation, which was shown immunohistochemically to be restricted to the dentate granule cells and their processes. The maximum decline in CaBP varied with the different kindling sites: perforant path, 33%; commissural path, 32%; septum, 30%; amygdala, 18%; and olfactory bulbs, 15%. There were no changes in the CaBP content of the stimulated areas themselves. In cases where the kindling stimulus was delivered unilaterally (perforant path and amygdala), the maximum decrease in hippocampal CaBP was observed ipsilateral to the site of stimulation when the criterion for full kindling was established (six consecutive stage 5 motor seizures). Further kindling trials were required to produce a similar magnitude decrease in the CaBP content of the contralateral hippocampus. These observations are discussed both in relation to the possible role of CaBP in the establishment of a seizure response to kindling and also as a potential compensatory mechanism that may serve to overcome the epileptogenic effects of kindling.

Parvalbumin and vitamin D-dependent calcium-binding protein (Mr 28,000): comparison of their localization in the cerebellum of normal and rachitic rats

Two neuronal and Ca2+-binding proteins, parvalbumin and a vitamin-D-dependent calcium-binding protein (CaBP; Mr = 28,000) were localized immunohistochemically in the rat cerebellum, which is the brain region containing the highest concentration of them both. Parvalbumin was present in Purkinje, basket and stellate cells of the molecular layer, whereas CaBP was only present in Purkinje cells. The concentrations of both proteins, measured immunohistochemically and biochemically, were unaffected by the vitamin D status of the rats.

Ultrastructural localization of the calcium-binding protein parvalbumin in neurons of the song system of the zebra finch, Poephila guttata

The distribution of parvalbumin (PV) within neurons of the vocal motor nucleus hyperstriatum ventralepars caudalis (HVc) was investigated in the forebrain of adult male zebra finches by means of light and electron microscopy using the indirect immunoperoxidase technique. Parvalbumin-reaction product was located in the amorphous material of perikarya, dendrites and nuclei, and associated to microtubuli, postsynaptic densities and intracellular membranes; it was found in some axons and Gray type-2 boutons, but rarely in type-1 boutons and never in the Golgi apparatus. These observations suggest that parvalbumin may regulate calcium-dependent processes at the postsynaptic membrane and in the cytosol. Furthermore, the partial association of parvalbumin to microtubuli points to an involvement in calcium-dependent tubular functions. Calcium currents and microtubular assembly or transport may be relevant for the known functions of HVc in song learning.