Hisao Yamada

Topographical Distribution of Neurons Containing Endothelin Type A Receptor in the Rat Brain

Endothelin (ET) was originally identified as a vasoactive peptide biosynthesized in vascular endothelial cells. Because ET has also been found in the brain as a neuropeptide, it has been thought to belong to the group of brain‐vascular peptide hormones. To date, type A and type B receptors for ET have been found. To elucidate the topographic distribution of type A receptor (ET‐AR) in the brain, we raised a specific antibody to the C‐terminal (64 amino acids) peptide of rat ET‐AR and immunostained rat brain sections with this antibody. Immunoreactivity for ET‐AR was detected in neuronal cell bodies and also in the many proximal and some distal parts of their fibers. Nerve cell bodies containing strong ET‐AR‐ immunoreactivity were distributed in the lateral part of the reticular formation, the nucleus of the solitary tract and its surrounding area, the dorsal midline area and medial longitudinal fasciculus, the subependymal layer of the fourth ventricular roof, the caudolateral area of the pontine tegmentum, the locus coeruleus, the rostral pontine area of the lateral reticular formation, the retrorubral area, the substantia nigra, the ventral tegmental area, the periventricular region lateral to the rostral mesencephalic aqueduct and caudal third ventricle, the arcuate hypothalamic nucleus, the caudomedial area of the zona incerta, the periventricular hypothalamic nucleus, the parvocellular portion of the paraventricular hypothalamic nucleus, and the periglomerular region of the olfactory bulb. In addition, the Purkinje cells of the cerebellar cortex, the nerve cells in the mesencephalic trigeminal nucleus, and the magnocellular neurons of the supraoptic and paraventricular hypothalamic nuclei showed weak immunoreactivity. The distribution of highly ET‐AR‐immunoreactive neurons is quite similar to that of catecholamine neurons. J. Comp. Neurol. 389:348–360, 1997.

Distribution of the endogenous digitalis-like substance (EDLS)-containing neurons labeled by digoxin antibody in hypothalamus and three circumventricular organs of dog and macaque

Endogenous digitalis-like substance (EDLS) is a newly discovered humoral agent which causes sodium-diuresis. EDLS is well known to have inhibitory activity to Na+,K(+)-ATPase and cross-immunoreactivity to digoxin antibody; however, its precise chemical structure has not yet been determined. We had previously developed a histochemical technique for EDLS, i.e., digoxin-immunohistochemistry, and demonstrated that EDLS was produced in the hypothalamic neurons. In the present study, the distribution of EDLS-containing neurons in the hypothalamus of dog and macaque was investigated using this technique, because anti-EDLS antibody cannot be obtained yet. In both species, EDLS neuronal somata were mainly localized in the paraventricular nucleus and the supraoptic nucleus and its accessory nuclei. A number of somata were also scattered in the other hypothalamic areas. The processes of these neurons ran from the area where the somata were located, through the lateral and basal area of the hypothalamus, to the infundibulum. These nerve fibers with varicosities were associated with the primary capillaries of hypophysial portal veins. A few immunopositive nerve fibers were also seen in the pituitary posterior lobe of both species. Intensive immunoreactivities were observed in the subfornical organ and organum vasculosum laminae terminalis. There were no differences between dog and macaque.

Immunohistochemical demonstration of serotonin-containing CSF-contacting neurons in the submammalian paraventricular organ

SummaryThe distribution and morphological aspects of the serotonin-containing neurons in the paraventricular organ of the carp, frog, turtle and chicken were studied by means of an immunoperoxidase technique using serotonin antiserum. In all species the serotonin-containing neurons were seen to have the appearance of the CSF-contacting neurons and to be distributed in the pars ependymalis and the pars hypendymalis of the organ. Particularly, in the frog, the serotonin-containing CSF-contacting neurons, mostly bipolar in shape, were also observed in the pars distalis. Their proximal processes protruded into the ventricular lumen through the ependymal layer with a globular- and triangular-shape. The distal processes projected ependymofugally to the pars distalis and formed a fine plexus in the neuropil of this part. The density of the serotonin fibers in the pars distalis was greater in the carp than in the other species.

Immunohistochemical demonstration of serotonin nerve fibers in the subthalamic nucleus of the rat, cat and monkey

Distribution of serotonin-immunoreactive nerve fibers (5-HT fibers) in the subthalamic nucleus (STN) of the rat, cat and monkey was examined with a modified peroxidase-anti-peroxidase method using 5-HT antiserum without pretreatment. Fine varicose 5-HT fibers formed a fine network in the STN. Overall density of 5-HT fibers in the STN was highest in the monkey, and lowest in the rat. In the rat and cat, these fibers were distributed almost diffusely in the STN, whereas in the monkey they were particularly abundant in the ventral and medial parts of the STN. Many thick 5-HT fibers ran through the monkey STN.

Pressor Response to Compression of the Ventrolateral Medulla Mediated by Glutamate Receptors

The rostral ventrolateral medulla (RVLM) is considered a major center for the regulation of sympathetic and cardiovascular activities. Several clinical studies have indicated a possible causal relationship between neurovascular contact of the left RVLM and essential hypertension, and some investigators have suggested that the left RVLM is more sensitive to pulsatile compression than the right RVLM. Previously, we reported that pulsatile compression of the RVLM elevates arterial pressure by enhancing sympathetic outflow in rats; however, we have not investigated the laterality of the responses to the compression. In addition, it remains to be elucidated whether RVLM neurons are activated by compression and, if so, how they are activated. Therefore, we performed compression experiments in rats to investigate these issues. Pulsatile compression was performed on the unilateral RVLM with a pulsating probe in anesthetized and artificially ventilated rats. Pulsatile compression of the unilateral RVLM increased arterial pressure, heart rate, and sympathetic nerve activity. The pressor response to compression was inhibited significantly after local microinjection of glutamate receptor antagonists. Pulsatile compression of the RVLM increased Fos immunoreactivitiy, a marker of neuronal activation, within the nuclei of postsynaptic RVLM neurons. All results were observed symmetrically. The data indicate that the responses to pulsatile compression of the unilateral RVLM are similar on both sides. They also suggest that pulsatile compression of the RVLM increases sympathetic and cardiovascular activities by activating postsynaptic RVLM neurons through the stimulation of the local glutamate receptors in rats.

Immunohistochemical demonstration of serotonin nerve fibers in the corpus striatum of the rat, cat and monkey.

SummaryThe distribution of serotonin-containing nerve fibers in the corpus striatum of the rat, cat and monkey was studied with modified peroxidase-antiperoxidase method using serotonin antiserum without any pretreatment. In the neostriatum (caudate nucleus and putamen) of all mammalian species investigated, the immunoreactive fibers were distinct varicose fibers in a fine network. The concentration of these fibers was high in the ventral, medial and caudal neostriatum. Especially in the area bounded by the globus pallidus, serotonin fibers were abundant and compactly arranged along the nucleus. In this area of the monkey, a few thick fibers (tract fibers) were intermingled; they ran along the lateral medullary lamina. Such tract fibers were also observed outside the medial medullary lamina and in the central portion of the medial pallidal segment. The paleostriatum (globus pallidus and entopeduncular nucleus) of the rat and cat as well as the medial pallidal segment of the monkey was diffusely innervated with serotonin fibers composed of numerous varicosities and fine intervaricose segments, while in the lateral pallidal segment of the monkey, the distribution of fibers was scantly and partial. Our results hint at the morphological basis of the serotonergic regulation of the extrapyramidal system in mammals.

Immunohistochemical Studies of the Serotonergic Supraependymal Plexus in the Mammalian Ventricular System, with Special Reference to the Characteristic Reticular Ramification

Distributional and morphological features, especially characteristics of the ramification of serotonin-containing supraependymal fibers (SEF), were studied in the ventricular systems of mammals (mouse, rat, guinea pig, rabbit, cat, dog, monkey) by means of a modified peroxidase antiperoxidase technique, using antiserotonin antiserum prepared in our laboratory. SEF were present in all ventricular systems, except on the third ventricle floor and in the choroid plexus. The density of SEF was higher in the smaller species. In the rat, light- and scanning electron microscopical SEF were almost completely abolished 1 week after intraventricular administration of 5,6-dihydroxytryptamine. Ramification of SEF was complicated; the SEF formed a true network with frequent anastomosing. In the ventricular system of rats rendered hydrocephalic by kaolin administration, the mode of axonal branching in the supraependymal plexus could best be analyzed by the scanning electron microscope because the meshes of the plexus were spread out.

Immunohistochemical studies on the serotonergic innervation of the pia mater

SummaryThe direct innervation of the pial blood vessels by serotonin neurons has been demonstrated with a modified peroxidase-antiperoxidase technique in the mammalian central nervous system. The pia mater covering the ventrolateral surface of the medulla oblongata is innervated by numerous varicose serotonin fibers originating from the serotonin neurons of the lower brainstem. Scattered serotonin fibers were observed in the pia mater in every part of the brain and spinal cord.

Immunohistochemical demonstration of serotonin nerve fibers in the cat neurohypophysis

SummaryDistribution of the serotonin nerve fibers in the neurohypophysis of adult cats was demonstrated using the peroxidase-antiperoxidase method. The serotonin nerve fibers were distributed in the internal and external layers of the infundibulum, terminating on the wall of the capillary loops and the outer surface of the external layer. A small number of the fibers scattered about in the posterior lobe penetrated the intercellular spaces in the intermediate lobe.

Simultaneous detection of B-cells and T-cells by a double immunohistochemical technique using immunogold-silver staining and the avidin-biotin-peroxidase complex method

SummaryA new double immunohistochemical technique for the simultaneous detection of B-cells and T-cells was investigated, using tissue preparations obtained from human axillary lymph nodes and rejected renal allografts. The specimens were immunostained first for the demonstration of B-cells, by the immunogold-silver staining (IGSS) method using Leu-12 monoclonal antibody, and then for T-cells by the avidin-biotin-peroxidase complex (ABC) method using Leu-1 monoclonal antibody. With the present methods, both B-cells and T-cells were clearly detected and distinctively identified without cross-linking of antibodies or double reaction of enzymes.