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C Leranth

Publications and source records attributed to C Leranth.

107 records · Page 6Linked to original sources
PubMed1988

Immunohistochemical evidence for synaptic connections between pro-opiomelanocortin-immunoreactive axons and LH-RH neurons in the preoptic area of the rat.

Connections between adrenocorticotropic hormone (ACTH)-immunoreactive neurons in the arcuate nucleus and the preoptic area were studied in the female rat. ACTH-immunopositive terminals were observed in the medial preoptic area in contact with dendritic shafts, while in the ventrolateral preoptic area the majority of ACTH-immunoreactive synapses were found on dendritic spines. Double-label electron microscopic immunocytochemistry using peroxidase and avidin-ferritin as contrasting electron-dense markers revealed numerous synaptic contacts between ACTH-immunopositive boutons and luteinizing hormone-releasing hormone (LH-RH)-immunoreactive dendritic shafts in the medial preoptic area. Following injection of horseradish peroxidase (HRP) into the medial preoptic area, retrogradely HRP-labeled perikarya were observed throughout the arcuate nucleus. Double-staining experiments revealed that a proportion of these retrogradely labeled cells, in the ventromedial arcuate nucleus, are also immunoreactive for ACTH. These results suggest that pro-opiomelanocortin peptide-producing neurons in the ventromedial arcuate nucleus project to the medial preoptic area. Some of these neurons establish direct synaptic contacts with LH-RH-immunoreactive cells.

Adrenocorticotropic Hormone↗
PubMed1988

Immunocytochemical evidence for direct synaptic connections between corticotrophin-releasing factor (CRF) and gonadotrophin-releasing hormone (GnRH)-containing neurons in the preoptic area of the rat.

Electron microscopic double-label immunostaining with peroxidase and avidin-ferritin was used to study connections between corticotrophin-releasing factor (CRF) and gonadotrophin-releasing hormone (GnRH) immunoreactive elements in the medial preoptic area of the rat. Synaptic contacts were observed between CRF-immunoreactive axon terminals and the dendrites of GnRH-immunopositive neurons. These results suggest that the inhibitory effects of stress-induced CRF release on reproductive function may involve a direct CRF input to the GnRH-producing cells.

Animals↗
PubMed1988

Catecholaminergic innervation of pyramidal and GABAergic nonpyramidal neurons in the rat hippocampus. Double label immunostaining with antibodies against tyrosine hydroxylase and glutamate decarboxylase.

This study describes the catecholaminergic innervation of rat hippocampal neurons at the electron microscopic level by using an antibody against tyrosine hydroxylase (TH) and immunocytochemical techniques. In a first series of experiments, the course and distribution as well as the synaptic contacts of TH-immunoreactive fibers were analyzed with the peroxidase-antiperoxidase (PAP) method. Next, peroxidase immunostaining of TH fibers was combined with glutamate decarboxylase (GAD) immunostaining, using avidinated ferritin as a second electrondense marker. Our results demonstrate that TH-immunostained terminals establish asymmetric synaptic contacts with spines of pyramidal neurons, and symmetric synaptic contacts with cell bodies and dendritic shafts of ferritin-labeled GAD-immunoreactive nonpyramidal cells.

Animals↗
PubMed1988

CCK-immunoreactive terminals form different types of synapses in the rat and monkey hippocampus.

Electronmicroscopic immunocytochemical analysis of the types and patterns of synaptic contacts formed by cholecystokinin (CCK)-containing terminals in the CA1 and CA3 region of the rat and monkey hippocampus reveals numerous symmetric synaptic contacts on cell bodies and dendritic shafts of pyramidal cells in both species. In the monkey, however, CCK-immunoreactive terminals also form asymmetric synaptic contacts with dendritic spines, such contacts are absent or very rare in the rat hippocampus. The present finding in primate hippocampus provides evidence that the same neuropeptides can be found in both symmetric and asymmetric contacts and may be added to other evidence challenging the traditional concept that symmetric synapses mediate exclusively inhibitory and asymmetric exclusively excitatory transmission. Furthermore, although our comparative analysis confirms considerable similarities in the distribution of CCK-containing elements in primate and rodent hippocampus it also revealed a potentially important difference in synaptoarchitecture that should be taken into account in extrapolations from one species to the other.

Animals↗
PubMed1988

Catecholaminergic innervation of luteinizing hormone-releasing hormone and glutamic acid decarboxylase immunopositive neurons in the rat medial preoptic area. An electron-microscopic double immunostaining and degeneration study.

Catecholaminergic innervation of luteinizing hormone-releasing hormone (LHRH) and glutamic acid decarboxylase (GAD) immunoreactive neurons in the rat medial preoptic area (MPO) was studied using electron-microscopic (EM) double-label immunostaining and combinations of single- and double-label immunostaining with acute axonal degeneration. The EM double-immunostaining experiments included double staining for either tyrosine hydroxylase (TH) and LHRH, or TH and GAD. Analysis of TH and LHRH double-immunostained material revealed synaptic connections between TH immunoreactive axons and LHRH immunopositive neurons. The TH and GAD double-staining experiments also demonstrated synaptic connections between axons immunoreactive for TH and GAD immunopositive neurons. Two days following unilateral surgical transection of the ventral and dorsal noradrenergic bundles, synaptic connections were found between degenerated boutons and GAD immunoreactive neurons in the ipsilateral MPO. However, no synapses could be observed in the same area between degenerated axons and the LHRH immunopositive neurons. Following the same operation and immunostaining for TH, a moderate number of degenerating TH axons as well as a large number of nondegenerated TH immunoreactive boutons were observed. Double immunostaining for TH and GAD in MPO sections ipsilateral to the operation revealed synaptic connections between the degenerating TH immunopositive axons and GAD immunoreactive neurons. These results suggest that there are direct synaptic connections between catecholaminergic axons and GAD and LHRH immunoreactive neurons in the medial preoptic area of the rat. Some of the connections between TH immunopositive afferents and GAD immunoreactive neurons may represent connections from noradrenergic neurons in the brain stem, while the majority of TH-GAD and TH-LHRH connections may represent innervation of GABA and LHRH neurons from local dopamine-containing cells.

Adrenergic Fibers↗
PubMed1987

GABAergic input of cholecystokinin-immunoreactive neurons in the hilar region of the rat hippocampus. An electron microscopic double immunostaining study.

Double immunostaining was performed for electron microscopy to analyze the synaptic connections between glutamate decarboxylase (GAD)-immunoreactive axons and cholecystokinin (CCK)-immunoreactive neurons in the hilar region of the rat hippocampal formation. Following immunostaining for CCK, the diaminobenzidine (DAB) reaction product was silver-intensified and gold-substituted. In a subsequent second immunostaining for GAD, the immunoreactive elements were labeled using a single DAB reaction. Electron microscopic analysis of the double-stained Vibratome sections demonstrated that the single DAB-labeled GAD-immunoreactive boutons form symmetrical synaptic connections on the soma and primary dendrites of the DAB-gold-labeled CCK-immunoreactive neurons.

3,3'-Diaminobenzidine↗
PubMed1987

Insulin specific binding sites in the myometrium of pregnant rats.

Insulin (INS) specific binding sites were detected in the myometrium of pregnant rats. The apparent equilibrium dissociation constants for the higher and lower affinity INS binding components were 0.01 X 10(-9) M and 2.5 X 10(-9) M, respectively. During the latter half of pregnancy INS binding increased gradually and peaked on the day of parturition (159.9 +/- 19.8, 196.3 +/- 24.6, 254.7 +/- 36.8, and 272.6 +/- 29.1 and femtomolars per mg protein, mean +/- SEM on days 15, 20, 21, and 22 of gestation, respectively). The pattern of increased INS binding paralleled the prepartum increase in myometrial cell nuclear estrogen receptors as well as myometrial glycogen levels. In contrast, low INS binding was associated with elevated cell nuclear progestin receptor levels, on day 15 and immediately postpartum. These results suggest that, during the latter half of pregnancy, myometrial INS binding capacity and glycogen concentration gradually increase. Since INS receptor levels begin to increase in parallel with increasing nuclear estrogen receptors, INS receptor synthesis may be under estrogen control.

Animals↗
PubMed1986

Synaptic connections of cholecystokinin-immunoreactive neurons and terminals in the rat fascia dentata: a combined light and electron microscopic study.

We report here on the fine structure and synaptic connections of neurons and axon terminals in the rat fascia dentata displaying immunoreactivity to antibodies against cholecystokinin octapeptide (CCK). In the fascia dentata and hilar region, CCK-immunoreactivity was confined to nonpyramidal neurons that were similar in appearance to basket cells known to use gamma-aminobutyric acid (GABA) as neurotransmitter. These neurons exhibited dense accumulations of endoplasmic reticulum and infolded nuclei, and established asymmetric and symmetric synaptic contacts with presynaptic terminals. Among those terminals that formed asymmetric synaptic contacts, giant mossy fiber boutons arising from granule cell axons were identified. Cholecystokinin-immunoreactive terminals established symmetric synaptic contacts on the cell bodies and dendrites of granule cells. Similar contacts were formed on nonimmunoreactive hilar neurons. Some of these hilar cells were identified as commissural neurons by retrograde filling with horseradish peroxidase (HRP) following injection of the tracer into the contralateral fascia dentata. Synaptic contacts were rarely observed between immunolabeled pre- and postsynaptic elements. The results are discussed with regard to inhibitory processes in the fascia dentata since other studies have shown that CCK is coexistent with GABA in hippocampal nonpyramidal neurons.

Animals↗
PubMed1986

GABAergic input to cholinergic forebrain neurons: an ultrastructural study using retrograde tracing of HRP and double immunolabeling.

Amygdalopetal cholinergic neurons in the ventral pallidum were identified by combining choline acetyltransferase (ChAT) immunohistochemistry with retrograde tracing of horseradish peroxidase (HRP) following injections of the tracer in the basolateral amygdaloid nucleus. Although ChAT-positive terminals were identified in the ventral pallidum, they were never seen in contact with either immunonegative or ChAT-positive amygdalopetal neurons. In material, in which immunostaining against glutamic acid decarboxylase (GAD), the synthesizing enzyme for GABA was combined with retrograde tracing of HRP from the basolateral amygdaloid nucleus, GAD-positive terminals were seen to contact immunonegative amygdalopetal neurons. In addition, when sections of the rostral forebrain were processed, first to preserve and identify the transported HRP, and then were sequentially tested for both ChAT and GAD immunohistochemistry with the immunoperoxidase reaction for both tissue antigens, GAD-immunopositive terminals were seen to make synaptic contacts with cholinergic amygdalopetal neurons. These results suggest that amygdalopetal, presumably cholinergic, neurons receive GAD-positive terminals. In separate experiments using immunoperoxidase for ChAT and ferritin-avidin for GAD labeling, we confirmed the presence of GAD-containing terminals on cholinergic neurons. In addition, cholinergic terminals were seen in synaptic contact with GAD-positive cell bodies. These morphological studies suggest that direct GABAergic-cholinergic and cholinergic-GABAergic interactions take place in the rostral forebrain.

Amygdala↗
PubMed1986

Reproductive failure due to experimentally induced constant estrus does not alter the LH-RH fiber density in the median eminence of the rat.

The effects of anterior hypothalamic deafferentation on luteinizing hormone releasing hormone (LH-RH) fiber density in the mediobasal hypothalamus (MBH) were compared to those of a number of nonsurgical treatments which give rise to anovulatory sterility (injections of estradiol valerate, exposure to constant light, or neonatal androgen administration) in the female rat. All of the treatments used (surgical and nonsurgical) disrupted the normal 4-day pattern of estrous cyclicity. Bilateral anterior hypothalamic deafferentation markedly reduced the packing density of LH-RH fibers in the MBH. Unilateral deafferentation reduced the number of fibers on the ipsilateral side of the MBH by 31-64% and on the contralateral side by 15-40%. In contrast, none of the three nonsurgical treatments had any significant effect on the LH-RH fiber density. Electron microscopic examination revealed no morphologic, or distribution differences in MBH LH-RH fibers between control females and animals rendered anovulatory by the nonsurgical experimental procedures. These results demonstrate that estrogen, androgen, and constant light induced anovulatory sterility are not associated with any overt change in the number or morphology of LH-RH immunoreactive fibers in the MBH, suggesting that the primary lesion responsible for the failure of normal estrous cyclicity in such animals resides in the systems responsible for regulating the activity of the LH-RH neurons rather than in the LH-RH neurons themselves.

Afferent Pathways↗
PubMed1985

Application of avidin-ferritin and peroxidase as contrasting electron-dense markers for simultaneous electron microscopic immunocytochemical labelling of glutamic acid decarboxylase and tyrosine hydroxylase in the rat arcuate nucleus.

A pre-embedding immunostaining procedure was developed using ferritin and peroxidase to enable simultaneous electron microscopic localization of two antigens in the same tissue section. This method was used to study the anatomic relationship between glutamic acid decarboxylase (GAD) immunoreactive axons and tyrosine hydroxylase (TH) - containing neurons of the rat arcuate nucleus. The findings provide ultrastructural evidence that GAD-immunoreactive terminals establish symmetric (Gray II) synapses on TH-reactive neurons.

Animals↗
PubMed1985

Choline acetyltransferase immunoreactivity is localized to four types of synapses in the rat interpeduncular nucleus.

The cholinergic synapses of the rat interpeduncular nucleus (IPN) were demonstrated by immunostaining that utilized a monoclonal antibody directed against choline acetyltransferase. The rostral, central, intermediate and lateral subnuclei of the IPN each contained a single type of immunoreactive terminal. Immunoreactivity was localized to synaptic vesicle membranes (especially at the contact zones), and longitudinal microtubules in preterminal portions of axons. Terminals were identified by comparison to previous studies of the synaptic organization of the IPN. In the rostral subnucleus, the immunoreactive terminals were characterized by their content of spherical vesicles, 45 nm in diameter, intermixed with moderate numbers of dense-cored vesicles, 75-100 nm in diameter. These terminals formed asymmetrical contacts. They correspond to the more numerous of the two types of axodendritic terminals described in this subnucleus, i.e. those which degenerate after lesions of the habenula. The moderate number of immunoreactive terminals in the lateral subnucleus contained pleomorphic vesicles, 30-45 nm in diameter. Up to three of these formed symmetrical contacts with individual dendrites, which ranged in diameter from 0.35 to 0.55 micron. The other types of axodendritic terminal in this subnucleus, which often contacted the same dendrites, were unstained. These latter terminals have been interpreted as being those which contain substance P. The immunoreactive terminals in the diameter, and formed markedly asymmetrical en passant contacts with small dendritic processes or spines. The immunoreactive terminals in the intermediate subnucleus had the same presynaptic and contact morphology. Many were clearly crest synapses. The remainder appeared to be such, but seen only partially within the plane of section. In the intermediate subnucleus there were up to several hundred immunostained terminals per grid square in some sections. These findings are consistent with the existence of a dense cholinergic projection to the IPN. The habenular region, are shown to crest and S synapses, both of which generate after lesions of the cholinergic innervation of other subnuclei of the IPN increases understanding of the relation of cholinergic to other transmitters localized to various portions of this nucleus.

Animals↗
PubMed1983

Fine structure of serotonin-containing axons in the marginal zone of the rat spinal cord.

Descending serotoninergic systems in the spinal cord may be involved in antinociception. In this study 6 rat spinal cords were prepared for serotonin immunostaining and marginal zones (lamina I of Rexed) from the dorsal horn were examined with electron microscopy. Stained terminals were often seen to be closely associated with the somata of lamina I neurones or other unstained axon terminals, but seldom formed conventional synaptic junctions. It is concluded that serotoninergic systems in this region may influence the activity of these associated structures in a diffuse non-synaptic manner.

Animals↗
PubMed1980

Ultrastructural investigation of ACTH immunoreactivity in arcuate and supraoptic nuclei of the rat.

Fine structural localization of an ACTH-like substance was obtained in neurons of the rat arcuate nucleus using immuno-electron microscopy, whereas it could not be confirmed that ACTH-containing cell bodies are present in the supraoptic nucleus. The immunoreactive cells of the arcuate nucleus appeared to be more numerous than the unreactive neurons. Immunostaining was carried out before embedding in resin. Empty vesicles of irregular shape were found in dendrites of immunoreactive arcuate neurons, but their significance and nature remain enigmatic. The reaction product was distributed uniformly throughout the cytoplasm of the ACTH-positive cells, except that the mitochondria, rough endoplasmic reticulum and Golgi vesicles and cisternae were devoid of PAP molecules. This distribution differed from the localization reported in ACTH-secreting cells of the rat anterior pituitary, where the reaction product was found in the rough endoplasmic reticulum and Golgi complex as well as in secretory granules.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Calcium-binding protein-containing neuronal populations in mammalian visual cortex: a comparative study in whales, insectivores, bats, rodents, and primates.

This study is focused on comparative analysis of gamma-aminobutyric acid-positive (GABAergic) neuronal populations in primary visual cortex of totally aquatic toothed whales and select terrestrial mammals with different evolutionary histories and various ecological adaptations. The distribution of neuronal populations containing the calcium-binding proteins calbindin and parvalbumin, which are recognized markers for the GABAergic neurons in cerebral cortex, is compared in five species of toothed whales and in representatives (one species each) of insectivores, bats, rodents, and primates. Computerized image analysis has shown that overall quantitative characteristics of GABAergic cortical neurons in toothed whales are similar to those in other mammalian orders. Thus, GABA-positive neurons represent 26% of the total population of cortical neurons in the visual cortex of whales. Some 97% of GABA-positive cells contain calcium-binding proteins, which is numerically similar to these parameters found in primates and other mammals. On the other hand, the typology and laminar distribution of calcium-binding protein-containing neurons in the primary visual cortex of five whale species (Delphinapterus leucas, Globicephala melaena, Phocoena phocoena, Stenella coeruleoalba, and Tursiops truncatus) differ significantly from those of primates (Macaca mulatta) and rodents (Rattus rattus) and are similar to those found in insectivorous bats (Eptesicus fuscus) and hedgehogs (Erinaceus europaeus). In whales, bats, and hedgehogs a significant concentration of calbindin-positive, vertically oriented bipolar and bitufted neurons was found in layers I, II, and IIIc/V with their axons arranged in a three-dimensional network. In primates and rodents they are distributed evenly across all cortical layers and are predominantly multipolar or bitufted neurons found in all cortical layers with their axons oriented along the vertical axis of the cortical plate. The parvalbumin-positive neurons in all mammalian species, including toothed whales, are represented by variously sized multipolar non-pyramidal cells. As opposed to all other mammalian species, the major concentrations of parvalbumin-positive neurons in whales are found in layers IIIc/V and VI, whereas in other cortical layers there are only scattered parvalbumin-positive neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗