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Biomedical subjects

M Tohyama

Publications and source records attributed to M Tohyama.

At least 361 records · Page 20Linked to original sources
PubMed1989

Involvement of extracellular calcium and arachidonate in [3H] dopamine release from rat tuberoinfundibular neurons.

The mechanism of [3H]dopamine [( 3H]DA) release was investigated using primary cultures of dispersed cells from the rat tuberoinfundibular region, which contains tyrosine hydroxylase (TH)-like immunoreactive neurons. The calcium ionophore A23187 at 10 nM and above caused a significant and dose-dependent increase in [3H]DA release. In the presence of 50 microM A23187, [3H]DA release was detectable within 30 s and reached a plateau in 15 min. The induction of [3H]DA release by 50 microM A23187 was abolished by lowering the extracellular calcium concentration with 2 mM EDTA. Maitotoxin, another calcium-channel activator, also increased [3H]DA release at a concentration of 50 ng/ml. Exogenous additions of 100 mIU/ml phospholipase A2 and 10 microM arachidonate caused significant release of [3H]DA. Furthermore, A23187 stimulated [3H]arachidonate release from tuberoinfundibular dopaminergic (TIDA) neurons in a dose- and time-dependent manner. These results suggest that extracellular calcium and arachidonate are involved in the process of [3H]DA release from rat TIDA neurons.

Animals↗
PubMed1989

Immunohistochemical evidence that most rat corticotrophs contain beta-adrenergic receptors.

Cells bearing beta-adrenergic receptors (beta-AdRs) were found in the anterior lobe of the rat pituitary gland using antiserum generated against affinity-purified beta 2-AdRs, which also cross-reacts with beta 1-AdRs. beta-AdR-positive cells were sparsely distributed in the anterior pituitary gland. The ultrastructure of these cells was similar to that of corticotrophs. Subsequent analysis of adjacent serial sections indicated that 75% of the ACTH-positive cells were beta-AdR-positive. Our findings demonstrate the presence of beta-AdRs on pituitary corticotrophs, which provides an anatomical basis for the direct regulation of corticotroph secretions by beta-adrenergic agents.

Adrenocorticotropic Hormone↗
PubMed1989

Localization of glycine and beta-adrenergic receptors in the rat brain.

The localization of glycine (GR) and adrenergic receptors (AdR) was examined in the rat brain using a monoclonal antibody against the affinity purified glycine receptor and a polyclonal antibody against purified beta2-AdR. GR were concentrated in the lower brainstem, whereas no immunoreactivity was observed in the diencephalon and forebrain except in a few diencephalic nuclei. The highest density was found in the cranial motor nuclei, reticular formation, parabrachial area, dorsal and ventral cochlear nuclei, and dorsal and ventral tegmental nuclei. On the other hand, AdR were widely but unevenly distributed in the rat brain. The present study further showed the presence of AdR in catecholaminergic terminals in the hypothalamus.

Animals↗
PubMed1989

Localization and origins of calcitonin gene-related peptide containing fibres in the vestibular end-organs of the rat.

The distribution, origin and fine structure of nerve terminals immunoreactive to calcitonin gene-related peptide (CGRP) were investigated in the vestibular end-organs of the rat by means of immunocytochemistry. Dense plexus of CGRP-like immunoreactive (CGRPI) fibres were observed just beneath the sensory epithelial layers of the ampullary crista of the semicircular canal, and utricular and saccular maculae of the otolith organ. Some CGRPI fibres left the plexus to enter the sensory epithelial layer. Parasagittal transection of the brain just medial to the cochlear nucleus revealed the presence of a few CGPRI fibres in the vestibular end-organs ipsilaterally, indicating that these fibres originate in the central nervous system. A combination of retrograde tracing and immunocytochemistry was then used to identify the origins of CGRPI fibres found in the vestibular end-organs. After injection of fast blue dye (FB) into the vestibular cistern, CGRPI neurons in the area dorsolateral to the genu of the facial nerve were labelled by FB bilaterally. The present ultrastructural study has revealed that most of the CGRPI fibres in the vestibular end-organs form direct contacts with afferent nerve terminals which surround type I vestibular sensory cells.

Acoustic Maculae↗
PubMed1988

Ontogeny of calcitonin gene-related peptide-immunoreactive structures in the rat forebrain and diencephalon.

Ontogeny of the calcitonin gene-related peptide (CGRP)-containing structures was investigated in the forebrain and diencephalon of the rat by means of indirect immunofluorescence. CGRP-like immunoreactive (CGRP-IR) fibers first appeared at gestational day 18 (E18) in the primordia of the bed nucleus of the stria terminalis, central amygdaloid nucleus and posterolateral portion of the lateral hypothalamic nucleus. CGRP-IR fibers gradually increased in immunoreactivity and in number in these nuclei toward birth. A pronounced increase of CGRP-like immunoreactive fibers was found after birth in these nuclei and made very dense plexuses of fibers in adult animals. A few CGRP-IR fibers first appeared at the perinatal stage in the lateral septum, the most caudal portion of the caudate-putamen, and ventromedial and ventroposterior thalamic nuclei. Then the immunoreactive fibers increased and dense plexuses were present in these brain areas of the adult. A small number of immunoreactive fibers appeared at postnatal day 4-7 (P4-7) in the caudal insular cortex and ventromedial hypothalamic nucleus. A significant number of fibers was present in these areas of the adult. On the other hand, CGRP-like immunoreactivity in cell bodies was first detected with faint immunofluorescence at P4 in the anteromedial parts of the lateral hypothalamic area and ventromedial and ventroposterior thalamic nuclei. Thereafter CGRP-IR cells increased in immunoreactivity, and a significant number of cells was noted in these nuclei of the adult. In addition, CGRP-IR cells are identified in the medial amygdaloid nucleus, and medial preoptic area at P14. In conclusion, in the forebrain and diencephalon (1) CGRP-like immunoreactivity appears in fibers earlier than in cell bodies, suggesting that at least some of immunoreactive fibers originate from the lower brainstem, and (2) high density of CGRP-IR structures present in the brain at embryonic and early postnatal stages may indicate that CGRP could be an important factor involved in the developmental organization of the central nervous system.

Aging↗
PubMed1988

Adrenergic projection from the caudal part of the nucleus of the tractus solitarius to the parabrachial nucleus in the rat: immunocytochemical study combined with a retrograde tracing method.

The presence of an adrenergic projection from the nucleus of the tractus solitarius (NTS) to the parabrachial nucleus (PB) was demonstrated by the immunocytochemistry combined with a retrograde tracing method. Numerous neurons containing both phenylethanolamine N-methyltransferase, a marker for adrenaline, and wheat germ agglutinin-conjugated horseradish peroxidase, a retrograde tracer, were detected in the dorsolateral part of the NTS at the level of the area postrema after injection of the tracer into the dorsal PB.

Adrenergic Fibers↗
PubMed1988

Neuropeptide Y-immunoreactive neurons receive synaptic inputs from dopaminergic axon terminals in the rat neostriatum.

Double immunocytochemistry using peroxidase-antiperoxidase and protein A-gold was performed to determine whether neuropeptide Y (NPY) immunoreactive neurons receive synaptic inputs from catecholaminergic axon terminals in the rat neostriatum. Tyrosine hydroxylase-immunoreactive axons were found to be in synaptic contact with the somas and proximal dendrites of NPY-immunoreactive neostriatal neurons. These latter neurons were medium-sized and had indented nuclei, and thus were thought to be medium aspiny interneurons. Thus nigrostriatal dopaminergic neurons may monosynaptically influence striatal NPY neurons.

Animals↗
PubMed1988

Organization of histaminergic fibers in the rat brain.

Detailed information on innervation of the histaminergic system in the brain is essential to an understanding of the physiological roles of this system. In a previous immunocytochemical study with antihistidine decarboxylase (HDC) antibody, we detected extensive networks of histaminergic fibers in many areas of the rat brain (Watanabe et al., '84). In the present study, we improved the immunocytochemical procedure and examined the detailed distribution of histaminergic innervation in the rat brain with anti-HDC antibody. As reported previously, the highest concentrations of fibers were found in the hypothalamic nuclei and medial forebrain bundle. With the modified procedure, we detected more dense networks of HDC-immunoreactive (HDCI) fibers. Furthermore, we demonstrated for the first time the existence of HDCI fibers in other regions, namely, the thalamic nuclei, median eminence, fimbria of the hippocampus, habenular nuclei, superior colliculus, nucleus of the optic tract, parabrachial nuclei, mesencephalic trigeminal nucleus, superior, lateral, and spinal vestibular nuclei, posterior lobe of the hypophysis, and vascular organ of the lamina terminalis. We also found dense transverse fibers in the retrochiasmatic area and supraoptic decussation, which suggests bilateral innervation of the histaminergic system. These results indicate that innervation of the rat brain by the histaminergic system is more extensive than observed previously.

Animals↗
PubMed1988

Co-localization of substance P and Met-enkephalin-Arg6-Gly7-Leu8 in the intraspinal neurons of the rat, with special reference to the neurons in the substantia gelatinosa.

A double-labeling immunofluorescence technique was employed to investigate the co-localization of the functionally antagonistic neuropeptides, substance P and enkephalins, within intraspinal neurons of the rat. Anti-Met-enkephalin-Arg6-Gly7-Leu8 (Enk-8) antiserum was used as a marker of the preproenkephalin A neuron system. The observations were focused on the lumbar spinal cord. Co-localization was most prominent within neurons in the substantia gelatinosa, in which more than 95% of substance P-like immunoreactivity neurons showed Enk-8-like immunoreactivity. These double-labeled cells corresponded to 45% of Enk-8-like immunoreactive neurons in the same area. This suggests that SP/Enk-8 interaction occurs at the axon terminals of the substantia gelatinosa neurons. In deeper layers of the dorsal horn (laminae III, IV), only 14% and 6% of SP-like immunoreactive and Enk-8-like immunoreactive neurons were double labeled, respectively. Co-localization was also observed in neurons located in the laminae I, V, VII and X, suggesting concomitant involvement of these peptides in a variety of spinal cord functions.

Animals↗
PubMed1988

Calcitonin gene-related peptide- and substance P-immunoreactive nerve fibers in Meissner's corpuscles of rats: an immunohistochemical analysis.

The present study demonstrates that about 15% of the Meissner's corpuscles (MCs) of the rat glabrous skin of the feet contain one to two fibers immunoreactive for calcitonin gene-related peptide (CGRP), and that these fibers originate from the dorsal root ganglion. Double immunofluorescent cytochemical investigation has revealed that almost all the CGRP-immunoreactive (CGRPI) fibers in the MCs were immunoreactive for substance P. Subsequent immunoelectron microscopic analysis has demonstrated that the CGRPI fibers in the MCs are unmyelinated. In the course of passage through the MCs, no synaptic contact between the CGRPI fibers and underlying cells or non-CGRPI fibers was found.

Animals↗
PubMed1988

Neuropeptide- and neurotransmitter-related immunoreactivities in the developing rat olfactory bulb.

The development of neuropeptide and neurotransmitter-related immunoreactivities in the rat olfactory bulb were investigated immunohistochemically by using antisera raised against substance P (SP), cholecystokinin-8 (CCK), neurotensin (NT), leucine-enkephalin or methionine-enkephalin-Arg6-Gly7-Leu8 (ENK), somatostatin (SOM), neuropeptide Y (NPY) and tyrosine hydroxylase (TH). Results obtained for the adult olfactory bulb confirmed previous observations, except for SP-like immunoreactive (SP-IR) granule cells in the main olfactory bulb (MOB) and NT-IR neurons around the modified glomerular complex (MGC) (Teicher et al., Brain Res. 194:530-535, 1980). SP-, CCK- and NT-IR neurons were observed in the MOB of the rat fetus. SP-IR neurons also appeared in the accessory olfactory bulb (AOB). Among them, NT-IR neurons in the MOB and SP-IR neurons in the AOB were observed on embryonic day 16. SP- and CCK-IR neurons in the MOB appeared on embryonic day 18. Most of these neurons were presumed to be projecting neurons. SOM-, NPY-, ENK- and TH-IR neurons appeared in the newborn rats. The number and intensity of immunostaining of these neurons continued to increase with age, producing the adult pattern, except for NT-IR neurons in the MGC and SP-IR neurons in the mitral cell layer of the AOB, which were more numerous and intensely stained in young animals.

Animals↗
PubMed1988

Presence of a substance P-like immunoreactive neurone system from the parabrachial area to the central amygdaloid nucleus of the rat with reference to coexistence with calcitonin gene-related peptide.

An ascending neurone system containing substance P-like immunoreactivity (SPI) from the lateral parabrachial nucleus (PBL) to the central amygdaloid nucleus (AC) was detected. Destruction of the external subdivision of the PBL resulted in a marked ipsilateral reduction of SPI fibres in the AC, which suggests that SPI neurones project mainly ipsilaterally to the AC. This was supported by the findings that injection of biotin-wheatgerm agglutinin into the AC labelled many neurones in the ipsilateral external subdivision of the PBL. Simultaneous staining with antiserum showed that some of these neurones contain SP. Immunohistochemical double-staining revealed that almost all of the SPI neurones in the external subdivision of the PBL contained calcitonin gene-related peptide.

Amygdala↗
PubMed1988

Autoradiographic visualization in rat brain of receptors for omega-conotoxin GVIA, a newly discovered calcium antagonist.

Putative N-type voltage-sensitive calcium channels were localized autoradiographically in thaw-mounted rat brain slices using [125I]omega-conotoxin GVIA as a ligand. Density of the toxin binding sites were highly heterogeneous throughout the brain. The highest density of the binding sites was observed in the glomerular layer of the olfactory bulb, cerebral cortex, molecular layer of the hippocampus, amygdaloid complex, reticular part of the substantia nigra, molecular layer of the cerebellar cortex, and nucleus of the solitary tract. White matter tract regions such as the internal capsule, corpus callosum, fimbria of the hippocampus, fornix, and fasciculus retroflexus showed an extremely low density.

Animals↗
PubMed1988

Calcitonin gene-related peptide containing autonomic efferent pathways to the pelvic ganglia of the rat.

Indirect immunofluorescence method was employed to investigate the involvement of calcitonin gene-related peptide (CGRP) in the autonomic efferent innervations of the pelvic visceral organs of the rat. Cells labeled with Fast blue (FB) injected into the pelvic ganglia were observed in the sacral parasympathetic nucleus; about 30% of these neurons showed CGRP-like immunoreactivity. These CGRP-like immunoreactive neurons were located in the dorsomedial part of the sacral parasympathetic nucleus, extending their dendrites mediolaterally. FB-labeled cells were also found in the upper lumbar level (L1, L2) of the spinal cord. Some of these neurons also showed CGRP-like immunoreactivity. CGRP-like immunoreactive varicose fibers were seen in the pelvic ganglia surrounding individual ganglion cells. Considerable amount of these fibers were not affected by sensory deafferentation, so they probably originated from autonomic efferent neurons.

Animals↗
PubMed1988

Adrenal medullary cells transmute into dopaminergic neurons in dopamine-depleted rat caudate and ameliorate motor disturbances.

Adrenal medullary cell suspensions, derived from newborn rats (postnatal day 1-6), were implanted into the head of the caudate nucleus in 35 rats with unilateral 6-hydroxydopamine (6-OHDA) lesions in the nigrostriatal dopamine (DA) pathway. Behavioral recovery from Met-amphetamine induced circling, cell growth and morphological features (tyrosine hydroxylase positive cells), and release of adrenaline (Ad), noradrenaline (NA), DA, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were investigated for 40 weeks after transplantation. Met-amphetamine induced circling decreased significantly in 43% (15/35) of the rats. The decrease was concurrent with transmutation of the tyrosine hydroxylase-like immunopositive (THLI) cells into mature neurons that had abundant elongated neurites with varicosities and synapses on neuronal elements in the host caudate. In the absence of behavioral recovery (57%, 20/35) THLI cells were very scant. DA, DOPAC and HVA were reduced more than 90% in perfusates collected by in vivo dialysis from the striata of the animals that were not improved by transplant. These levels recovered to 20-50% of controls in animals whose behavior recovered. Ad and NA were not detected in the perfusates of either recovered or non-recovered animals. The results suggest that some grafted adrenal medullary cells transform into dopaminergic neurons and the release of DA from these grafted cells functionally affects behavior improvement for at least 40 weeks.

Adrenal Medulla↗