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PubMed1999

Calbindin D28k and calretinin in oxytocin and vasopressin neurons of the rat supraoptic nucleus.A triple-labeling immunofluorescence study

The aim of the present study was to examine quantitatively whether two calcium-binding proteins, calbindin D28k and calretinin, are localized in oxytocin and vasopressin neurons of the supraoptic nucleus of the male rat. We used a triple-labeling immunofluorescence method with a confocal laser scanning microscope. Of the oxytocin-labeled cells, 70% were stained for both calbindin D28k and calretinin, 15% were stained for only calbindin D28k, 13% were stained for only calretinin, and 2% were stained for neither protein. Of the vasopressin-labeled cells, 73% were stained for neither calbindin D28k nor calretinin, 21% were stained for only calbindin D28k, 4% were stained for only calretinin, and 2% were stained for both proteins. Calbindin D28k and calretinin have been shown previously to contribute to calcium homeostasis by buffering [Ca(2+)](i). Therefore, these findings suggest that most of the oxytocin neurons may have a higher Ca(2+)-buffering capacity than most of the vasopressin neurons.

Journal Article↗

PubMed1997

Two distinct subgroups of cholecystokinin-immunoreactive cortical interneurons.

Examination of cholecystokinin-immunoreactive cells in the rat frontal cortex revealed the presence in layers I-VI of a non-uniform population ranging in size from small to large. All were also immunoreactive for GABA. The most commonly observed dendritic form of the small cells were bipolar or bitufted although some were multipolar and demonstrated vasoactive intestinal polypeptide and in a few case calretinin immunoreactivity. The large cells were multipolar or bitufted and lacked expression of vasoactive intestinal polypeptide and calretinin immunoreactivity but occasionally showed calbindin D28k immunoreactivity. Therefore, the cholecystokinin-immunoreactive cells could be divided into two distinct subpopulations depending on their chemistry and morphology. Our previous studies showed that GABAergic cells in the neocortex could be classified into at least three chemically different subgroups: (1) parvalbumin-containing cells; (2) somatostatin-containing cells (most of them also contain calbindin D28k); and (3) vasoactive intestinal polypeptide- and/or calretinin-containing cells. The present results indicated that the small cholecystokinin-immunoreactive non-pyramidal cells constitute a subset of the vasoactive intestinal polypeptide- and/or calretinin-containing cortical GABAergic cells. The large cells remain to be categorized.

Animals↗

PubMed2000

Localization of the epithelial Ca(2+) channel in rabbit kidney and intestine.

The epithelial Ca(2+) channel (ECaC), which is exclusively expressed in 1,25-dihydroxyvitamin D(3)-responsive tissues, i.e., kidney, intestine, and placenta, is postulated to constitute the initial step in the process of transcellular Ca(2+) transport. To strengthen this postulated function, the present study compares the segmental and cellular distribution of ECaC and the other Ca(2+) transport proteins known to be involved in transcellular Ca(2+) transport. In rabbit kidney, ECaC mRNA and protein expression were primarily present in the connecting tubule. Immunopositive staining for the ECaC protein was exclusively found at the apical domain of this tubular segment. Importantly, ECaC completely colocalized with calbindin-D(28K), Na(+)-Ca(2+) exchanger (NCX), and plasma membrane Ca(2+) -ATPase (PMCA). A minority of cells along the distal tubule lacked immunopositive staining for ECaC and the other Ca(2+) transporting proteins. These negative cells were identified as intercalated cells. In intestine, ECaC was present in a thin layer along the apical membrane of the duodenal villus tip, whereas the crypt and goblet cells were negative. Again, a complete colocalization was observed between ECaC, calbindin-D(9K), and PMCA. In contrast to the kidney, NCX could not be detected in duodenum. The present finding that ECaC completely colocalizes with the Ca(2+) transport proteins in the connecting tubule and duodenum, together with its apical localization, further substantiates the postulated function of ECaC as the gatekeeper of active Ca(2+) (re)absorption.

Animals↗

PubMed1989

Extracellular calcium modulates vitamin D-dependent calbindin-D28K gene expression in chick kidney cells.

The effect of extracellular calcium ion (Ca2+) concentration on 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3)-induction of vitamin D-dependent calcium-binding protein (calbindin-D28K) and its mRNA levels was examined in primary chick kidney cells in vitro. When exposed to normal medium Ca2+ (1.0 mM), 1,25-(OH)2D3 increased calbindin-D28K mRNA, as measured by Northern analysis, by 4-10 fold over basal levels by 12 to 24 h after addition of hormone. In the presence of 0.5 mM Ca2+, 1,25-(OH)2D3 induced calbindin-D28K mRNA by only 2 fold, whereas, when cells were exposed to 2 mM Ca2+, the induction was 10-15 fold. This calcium modulation of 1,25-(OH)2D3 induction was also observed at the level of calbindin-D28K protein concentrations as measured by radioimmunoassay. The alterations in medium Ca2+ were not associated with any change in the rate of total RNA or protein synthesis. These studies suggest that both Ca2+ and 1,25-(OH)2D3 participate in the regulation of calbindin-D28K gene expression in the kidney.

Animals↗

PubMed2002

Suppression of death receptor signaling in cerebellar Purkinje neurons protects neighboring granule neurons from apoptosis via an insulin-like growth factor I-dependent mechanism.

Neuronal apoptosis contributes to the progression of neurodegenerative disease. Primary cerebellar granule neurons are an established in vitro model for investigating neuronal death. After removal of serum and depolarizing potassium, granule neurons undergo apoptosis via a mechanism that requires intrinsic (mitochondrial) death signals; however, the role of extrinsic (death receptor-mediated) signals is presently unclear. Here, we investigate involvement of death receptor signaling in granule neuron apoptosis by expressing adenoviral, AU1-tagged, dominant-negative Fas-associated death domain (Ad-AU1-deltaFADD). Ad-AU1-deltaFADD decreased apoptosis of granule neurons from 65 +/- 5 to 27 +/- 2% (n = 7, p < 0.01). Unexpectedly, immunocytochemical staining for AU1 revealed that <5% of granule neurons expressed deltaFADD. In contrast, deltaFADD was expressed in >95% of calbindin-positive Purkinje neurons ( approximately 2% of the cerebellar culture). Granule neurons in proximity to deltaFADD-expressing Purkinje cells demonstrated markedly increased survival. Both granule and Purkinje neurons expressed insulin-like growth factor-I (IGF-I) receptors, and deltaFADD-mediated survival of granule neurons was inhibited by an IGF-I receptor blocking antibody. These results demonstrate that the selective suppression of death receptor signaling in Purkinje neurons is sufficient to rescue neighboring granule neurons that depend on Purkinje cell-derived IGF-I. Thus, the extrinsic death pathway has a profound but indirect effect on the survival of cerebellar granule neurons.

Adaptor Proteins, Signal Transducing↗

PubMed1998

Significant elevation of urinary 28-kD calbindin-D and N-acetyl-beta-D-glucosaminidase levels in patients undergoing extracorporeal shock wave lithotripsy.

Calbindin-D, a vitamin D-dependent calcium binding protein with a molecular mass of 28 kD, is found predominantly in distal renal tubules and central nervous system tissues in man. We have developed a highly sensitive enzyme immunoassay for human 28-kD calbindin-D and demonstrated its advantages as a new marker for damage to distal renal tubules. Urinary N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme of the proximal renal tubules, is another segment-specific indicator of renal damage. To clarify whether both proximal and distal renal tubules are similarly affected by extracorporeal shock wave lithotripsy (SWL) treatment, urinary 28-kD calbindin-D and NAG were measured before, then immediately, 2 and 24 hours after SWL in 17 renal lithiasis patients. Levels of urinary calbindin-D were markedly elevated immediately and 2 hours after SWL and then decreased. In sera, levels of calbindin-D also increased, closely correlated with the changes in urinary values. Levels of urinary NAG were also significantly elevated immediately after SWL and then decreased. The results indicate that damage to both proximal and distal renal tubules occurs simultaneously with SWL and that the two markers can be applied as sensitive indicators of such side effects and their alleviation with protective agents.

Acetylglucosaminidase↗

PubMed1992

Regulation of calbindin mRNA and calbindin turnover in intestine and shell gland of the chicken.

A synthetic oligonucleotide was used as a probe for measurement of calbindin mRNA in the shell gland and intestine of chickens. The half time of calbindin mRNA in the duodenum and shell gland was estimated at 2 and 3.6 h and that of calbindin at 13.9 and 32.6 h, respectively. The formation rates of calbindin mRNA were 0.37 and 0.17 pmol.h-1.g-1 and the rate of calbindin formation was 0.099 and 0.031 microgram.pmol mRNA-1.h-1 in the duodenum and shell gland, respectively. In the shell gland, calbindin mRNA and calbindin appeared at the time of sexual maturation during calcification of the first egg shell. Calbindin mRNA fluctuated markedly during the daily egg cycle, in close temporal association with egg shell calcification. When Ca2+ deposition was eliminated by expulsion of the ovum, the rise in calbindin mRNA was prevented. An indirect suppression of Ca2+ deposition by administration of the carbonic anhydrase inhibitor acetazolamide also resulted in a decrease in calbindin mRNA. The results are consistent with a possible role of Ca2+ flux in the regulation of calbindin mRNA appearance in the shell gland of chickens.

Animals↗

PubMed1994

Calcium metabolic changes and calbindin-D in experimental hypertension.

OBJECTIVE: To examine renal and intestinal calbindin-D in relation to calcium metabolic changes in three different models of experimental hypertension. DESIGN: Spontaneously hypertensive rats (SHR), hypertension-prone Dahl salt-sensitive (Dahl-S) rats and the Goldblatt two-kidney, one clip rat model of renovascular hypertension were examined. RESULTS: Both prehypertensive and hypertensive SHR had significantly lower concentrations of both renal calbindin-D28k and intestinal calbindin-D9k than Wistar control rats. This was accompanied by hypocalcaemia, hypomagnesaemia and increased plasma 1,25(OH)2 vitamin D levels. Induction of hypertension in Dahl-S rats reduced intestinal calbindin-D9k and increased plasma levels of 1,25(OH)2 vitamin D, while renal calbindin-D28k levels, plasma calcium levels and plasma magnesium levels were unchanged. Renovascular hypertension was associated with a significant increase in the intestinal calbindin-D9k, plasma 1,25(OH)2 vitamin D, parathyroid hormone and magnesium levels, while renal calbindin-D2k, plasma calcium and phosphorus levels were unaffected. CONCLUSIONS: These three models of experimental hypertension have clearly demonstrated three separate patterns in the regulation of renal and intestinal calbindin-D, which relate to different alterations of factors involved in calcium and magnesium metabolism. In all three models hypertension was accompanied by a significant increase in plasma concentrations of 1,25(OH)2 vitamin D. Only rats with renovascular hypertension showed increased intestinal calbindin-D9k levels, whereas reduced concentrations were found in the SHR and in the hypertensive Dahl-S rats. This indicates the existence of a resistance at the cellular level to 1,25(OH)2 vitamin D affecting the expression of calbindin-D in both SHR and Dahl-S rats.

Animals↗

PubMed1991

Vitamin D and chick embryonic yolk calcium mobilization: identification and regulation of expression of vitamin D-dependent Ca2(+)-binding protein, calbindin-D28K, in the yolk sac.

The developing chick embryo acquires calcium from two sources. Until about Day 10 of incubation, the yolk is the only source; thereafter, calcium is also mobilized from the eggshell. We have previously shown that during normal chick embryonic development, vitamin D is involved in regulating yolk calcium mobilization, whereas vitamin K is required for eggshell calcium translocation by the chorioallantoic membrane. We have studied here the biochemical action of 1,25-dihydroxy vitamin D3 in the yolk sac by examining the expression and regulation of the cytosolic vitamin D-dependent calcium-binding protein, calbindin-D28K. Two types of embryos are used for this study, normal embryos developing in ovo and embryos maintained in long-term shell-less culture ex ovo, the latter being dependent solely on the yolk as their calcium source. Our findings are (1) calbindin-D28K is expressed in the embryonic yolk sac, detectable at incubation Days 9 and 14; (2) the embryonic yolk sac calbindin-D28K resembles that of the adult duodenum in both molecular weight (Mr 28,000) and isoelectric point, as well as the presence of E-F hand Ca2(+)-binding structural domains; (3) systemic calcium deficiency caused by shell-less culture of chick embryos results in enhanced expression of calbindin-D28K in the yolk sac during late development; (4) yolk sac calbindin-D28K expression is inducible by 1,25-dihydroxy vitamin D3 treatment in vivo and in vitro; and (5) immunohistochemistry revealed that yolk sac calbindin-D28K is localized exclusively to the cytoplasm of the yolk sac endoderm. These findings indicate that the chick embryonic yolk sac is a genuine target tissue of 1,25-dihydroxy vitamin D3.

Animals↗

PubMed1998

The three-dimensional structure of Ca(2+)-bound calcyclin: implications for Ca(2+)-signal transduction by S100 proteins.

BACKGROUND: Calcyclin is a member of the S100 subfamily of EF-hand Ca(2+)-binding proteins. This protein has implied roles in the regulation of cell growth and division, exhibits deregulated expression in association with cell transformation, and is found in high abundance in certain breast cancer cell lines. The novel homodimeric structural motif first identified for apo calcyclin raised the possibility that S100 proteins recognize their targets in a manner that is distinctly different from that of the prototypical EF-hand Ca2+ sensor, calmodulin. The NMR solution structure of Ca(2+)-bound calcyclin has been determined in order to identify Ca(2+)-induced structural changes and to obtain insights into the mechanism of Ca(2+)-triggered target protein recognition. RESULTS: The three-dimensional structure of Ca(2+)-bound calcyclin was calculated with 1372 experimental constraints, and is represented by an ensemble of 20 structures that have a backbone root mean square deviation of 1.9 A for the eight helices. Ca(2+)-bound calcyclin has the same symmetric homodimeric fold as observed for the apo protein. The helical packing within the globular domains and the subunit interface also change little upon Ca2+ binding. A distinct homology was found between the Ca(2+)-bound states of the calcyclin subunit and the monomeric S100 protein calbindin D9k. CONCLUSIONS: Only very modest Ca(2+)-induced changes are observed in the structure of calcyclin, in sharp contrast to the domain-opening that occurs in calmodulin and related Ca(2+)-sensor proteins. Thus, calcyclin, and by inference other members of the S100 family, must have a different mode for transducing Ca2+ signals and recognizing target proteins. This proposal raises significant questions concerning the purported roles of S100 proteins as Ca2+ sensors.

Animals↗

PubMed1991

Vitamin D-independent expression of chick brain calbindin-D28K.

A combination of calbindin-D28K-specific cDNA probes and polyclonal antisera were used to investigate expression of the calbindin-D28K in the vitamin D-deficient avian brain in vivo in response to pharmacological doses of the vitamin D3 metabolite, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Serum calcium levels were stimulated (2-fold) and intestinal calbindin-D28K expression (between 10- and 30-fold) by 1,25(OH)2D3 (6.5 nmol/animal) after 12 h. In marked contrast, steady-state whole brain levels of calbindin-D28K as judged by enzyme-linked immunoassay (ELISA) remained constant. Northern gel analysis revealed that three species of calbindin-D28K mRNA (2.0, 2.6 and 3.1 kb) were present a priori in the vitamin D-deficient chick brain and that administration of pharmacological doses (6.5 nmol/animal) of 1,25(OH)2D3 failed to influence their relative abundance. Separate but parallel dot blot hybridization analyses also confirmed that brain calbindin-D28K-mRNA levels were not influenced by 1,25(OH)2D3. These experiments demonstrate at the molecular level that, in contrast to the intestine, the gene encoding calbindin-D28K in the brain is regulated by mechanism(s) or factors which are independent of vitamin D status.

Animals↗

PubMed2005

Redox sensitive cysteine residues in calbindin D28k are structurally and functionally important.

Human calbindin D(28k) is a Ca(2+) binding protein that has been implicated in the protection of cells against apoptosis. In this study, the structural and functional significance of the five cysteine residues present in this protein have been investigated through a series of cysteine-to-serine mutations. The mutants were studied under relevant physiological redox potentials in which conformational changes were monitored using ANS binding. Urea-induced denaturations, as monitored by intrinsic tryptophan fluorescence, were also carried out to compare their relative stability. It was shown that the two N-terminal cysteine residues undergo a redox-driven structural change consistent with disulfide bond formation. The other cysteine residues are not by themselves sufficient at inducing structural change, but they accentuate the disulfide-dependent conformational change in a redox-dependent manner. Mass spectrometry data show that the three C-terminal cysteine residues can be modified by glutathione. Furthermore, under oxidizing conditions, the data display additional species consistent with the conversion of cysteine thiols to sulfenic acids and disulfides to disulfide-S-monoxides. The biological function of calbindin D(28k) appears to be tied to the redox state of the cysteine residues. The two N-terminal cysteine residues are required for activation of myo-inositol monophosphatase, and enzyme activation is enhanced under conditions in which these residues are oxidized. Last, oxidized calbindin D(28k) binds Ca(2+) with lower affinity than does the reduced protein.

Amino Acid Sequence↗

PubMed2004

Ca(2+) sensing receptor activation by CaCl(2) increases [Ca2+]i resulting in enhanced spatial interactions with calbindin-D28k protein.

The extracellular calcium ion concentration, [Ca2+]o, sensing receptor CaR is a G-protein coupled membrane receptor and it is involved in regulating cell proliferation, differentiation, secretion, and apoptosis. Calbindin-D28k is a high affinity calcium-binding protein that plays important roles in modulating the intracellular calcium ion concentration, [Ca2+]i, and thus influences signal transduction. The role of CaR in sensing and responding to [Ca2+]o and spatial interactions of CaR with calbindin-D28k in a distal tubule-like renal cell line are described. Fura-2 loaded Madin Darby bovine kidney (MDBK) cells were exposed to increasing concentrations of CaCl2 and the [Ca2+]i was determined by ratio fluorescence microscopy. The step-wise addition of CaCl2 caused continual increase in [Ca2+]i. The thapsigargin induced increase in [Ca2+]i observed in basal medium was eliminated by pretreatment of MDBK cells with 10 mM CaCl2 thereby suggesting the involvement of endoplasmic reticulum Ca2+ stores in increasing the [Ca2+]i. CaR was localized in the plasma membrane by using confocal microscopy. The confocal microscopy data also showed CaR and calbindin-D28k were co-localized when cells were exposed to 40 mM CaCl2. We postulate that sensing and responses to increasing [Ca2+]o that occur through CaR, increase the [Ca2+]i causing the translocation of Ca2+-bound calbindin-D28k towards CaR.

Animals↗

PubMed2000

Histamine suppresses A-type potassium current in myenteric neurons from guinea pig small intestine.

Perforated patch-clamp methods for recording ionic currents in the whole-cell configuration were used to test the hypothesis that the ionic mechanisms for the excitatory actions of histamine on enteric neurons include suppression of A-type K(+) current (I(A)). Histamine and the selective histamine H(2) receptor agonist, dimaprit, reduced the amplitude of I(A) without affecting the slope factor for I(A) steady-state inactivation curves. Suppression of I(A) was restricted to after hyperpolarization-type myenteric neurons that were immunoreactive for calbindin. The selective histamine H(2) receptor antagonist cimetidine suppressed the action of histamine and dimaprit. Elevation of intraneuronal cAMP by forskolin, a membrane-permeant analog of cAMP, and treatment with a phosphodiesterase inhibitor suppressed I(A.) The results are consistent with the hypothesis that suppression of I(A) is part of the ionic mechanism responsible for elevation of excitability during both slow synaptic excitation and slow synaptic excitation-like responses evoked by paracrine mediators, such as histamine, in after hyperpolarization-type myenteric neurons.

Animals↗

PubMed2006

Dual role of calbindin-D28K in vesicular catecholamine release from mouse chromaffin cells.

Calbindin-D(28K) is suggested to play a postsynaptic role in neurotransmission and in the regulation of the intracellular Ca(2+) concentration. However, it is still unclear whether calbindin-D(28K) has a role in the regulation of exocytosis, either as Ca(2+) buffer or as Ca(2+) sensor. Amperometric recordings of catecholamine exocytosis from wild-type and calbindin-D(28K) knockout mouse chromaffin cells reveal a strong reduction in the number of released vesicles, as well as in the amount of neurotransmitter released per fusion event in knockout cells. However, Ca(2+) current recordings and Ca(2+) imaging experiments, including video-rate confocal laser scanning microscopy, revealed that the intracellular Ca(2+) dynamics are remarkably similar in wild-type and knockout cells. The combined results demonstrate that calbindin-D(28K) plays an important and dual role in exocytosis, affecting both release frequency and quantal size, apparently without strong effects on intracellular Ca(2+) dynamics. Consequently, the possibility that calbindin-D(28K) functions not only as a Ca(2+) buffer but also as a modulator of vesicular catecholamine release is discussed.

Adrenal Medulla↗

PubMed1992

Age-related alterations in calbindin-D28K induction by 1,25-dihydroxyvitamin D3 in primary cultures of rat renal tubule cells.

In vivo studies have indicated that renal calbindin-D28K protein and mRNA levels decrease in adult and old rats, and this decrease parallels the age-associated decline in serum 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] levels. However, diminished renal responsiveness to 1,25-(OH)2D3 with advancing age could also contribute to decreased calbindin-D28K expression. To study renal responsiveness with age, primary cell cultures were established from the kidney cortices of young (1 month old), adult (10-12 months old), and old (20-24 months old) rats. Cells were incubated in medium K-1 containing 2% fetal calf serum. Calbindin-D28K protein levels were determined by Western blot and enzyme-linked immunosorbent assay. In young animals, the levels of calbindin-D28K declined from 12.1 +/- 1.3 micrograms/mg protein in the intact kidney to 1.6 +/- 0.07 micrograms/mg protein in cells that had been cultured for 3 days in the absence of 1,25-(OH)2D3. This sharp decline in calbindin-D28K protein concentration moderated by days 6-8. The continuous presence of 10(-7) M 1,25-(OH)2D3 in the medium did not abolish the decline. The low levels of calbindin-D28K in the cells cultured in the absence of 1,25-(OH)2D3 provided an excellent experimental system in which to compare the response of the cells to 1,25-(OH)2D3 between age groups. In cultured cells treated with 1,25-(OH)2D3 for 72 h, calbindin-D28K induction was greater in cells from adult and old animals compared to cells from young animals. The ratios of calbindin-D28K content (with vitamin D/without vitamin D) were 2.2 +/- 0.2, 4.7 +/- 0.5, and 7.1 +/- 1.5 for young, adult, and old cells, respectively. These studies suggested that the observed in vivo decrease in renal calbindin-D28K with age is primarily due to the lowered circulating 1,25-(OH)2D3.

Aging↗

PubMed1999

Anterograde tracing and immunohistochemical characterization of potentially mechanosensitive vagal afferents in the esophagus.

Vagal mechanosensitive afferents with an important functional role in esophageal peristalsis are well known from physiological studies. It is not known whether these fibers represent a separate subpopulation among all vagal afferents projecting to the esophageal wall. A morphological and immunohistochemical description of vagal afferents was undertaken to define their possible homo- or heterogeneity. The peripheral projections of vagal afferents were anterogradely labeled by injection of wheatgerm agglutinin conjugated to horseradish peroxidase into the nodose ganglion of rats. The anterogradely transported tracer was detected by tyramide amplification in conjunction with immunohistochemistry for Ca(2+)-binding proteins recently identified in different types of mechanosensory endings. It was found that vagal afferents represented a morphologically and structurally homogeneous population projecting to the myenteric ganglia of the esophagus, where they terminated as highly branched endings. Vagal afferent terminals, however, were different in their staining intensity for calretinin and calbindin, which ranged from intense to no detectable immunofluorescence. The fluorescence intensity of Ca(2+)-binding proteins within the vagal terminating branches was graded and the average staining intensity determined of all terminating branches in the upper, middle, and lower thirds of the esophagus. The average staining intensity was highest in the upper third of the esophagus and then declined in a statistically significant manner in the middle and lower thirds. This result suggests different requirements for intracellular Ca(2+)-buffering capacities in vagal afferents depending on their position along the esophageal axis and corroborates studies reporting a segmental organization of esophageal motility. Immunohistochemical evidence of substance P (SP) in a subset of vagal terminals was demonstrated. Hence, an effector role of vagal afferents on esophageal peristalsis by the release of SP, as has been proposed by physiological studies, is also supported by immunohistochemical data.

Animals↗

PubMed1993

Comparative distribution of calbindin and Met-enkephalin immunoreactivities in the guinea-pig lateral septum, with reference to electrophysiologically characterized neurons in the mediolateral part.

The distribution both of Met-enkephalinergic nerve terminals and of calbindin-containing neurons was investigated in the guinea-pig lateral septum, using a double-immunostaining technique. The findings show that the two immunoreactivities overlapped for neurons located in areas of the dorsal part and of the mediolateral part of the lateral septum. Nine cells of the mediolateral part which were electrophysiologically characterized and intracellularly labelled were subjected to the double-immunostaining protocol. All these cells displayed characteristic discharges due to the activation of high-threshold Ca2+ conductances. Two of them contained calbindin and were the target of enkephalinergic inputs; they possessed somatic spines. These data demonstrate: (1) that the guinea-pig lateral septum contains subpopulations of calbindin neurons which are postsynaptic to enkephalinergic inputs; (2) that Ca2+ conductances are not related to the presence of calbindin; (3) that somatospiny neurons, which are involved in the regulation of the hippocampo-septo-hypothalamic complex, contain calbindin and are the target of enkephalinergic endings.

Animals↗