Tadao Matsuura

Serotonergic innervation on the motoneurons in the mammalian brainstem

SummaryA comparative study of serotonergic innervation on motoneurons in the brainstem of various mammals (mouse, rat, guinea pig, dog, cat and monkey) was carried out using a sensitive immunohistochemical method. Except for the extraocular muscle nuclei, the motor nuclei of the cranial nerves received rich inputs from serotonin neurons, in all species examined — rodent, carnivore and primate. The motoneurons of the monkey were innervated by varicose serotonin fibers, in a manner different from that of other species, i.e. their cell bodies and proximal dendrites were tightly encircled by a large number of serotonin-containing varicose fibers. At the ultrastructural level, a predominant population of axosomatic contacts was confirmed in the cranial motor nuclei of the monkey, particularly in the nucleus ambiguus.

Light and electron microscopic immunohistochemical studies of serotonin nerve fibers in the substantia nigra of the rat, cat and monkey

SummaryThe distribution of serotonin-containing nerve fibers in the substantia nigra of the rat, cat and monkey was studied with a highly sensitive peroxidase-antiperoxidase immunohistochemical method. Serotonin fibers in the substantia nigra of all species consisted of fine varicose fibers and formed a fine network. In the zona compacta of all species, serotonin fibers were sparsely distributed. In the zone reticularis of the rat and cat, these fibers were densely distributed and their distributional pattern was almost uniform, while in the monkey such fibers were unevenly distributed and high and low dense areas were intermingled. In the pars lateralis of all species, serotonin fibers were diffusely distributed, and the distributional density was much higher in the cat and monkey than in the rat. Immunoelectron-microscopic studies further revealed that a majority of the labeled varicosities in the rat substantia nigra were in close apposition to peridendritic axon terminals and were also free in the neuropil; occasionally they exhibited symmetrical synapses of “en passant” type with non-immunoreactive dendrites or somata. Our results support a functional significance of serotonergic regulation of the substantia nigra in mammals.

Immunohistochemical Demonstration of the Organization of Serotonin Neurons in the Brain of the Monkey (Macaca fuscata)

The distribution and morphological characteristics of the perikarya of serotonin (5-HT) neurons in the brain of the monkey ( Macaca fuscata ) were studied using a peroxidase-antiperox

Characteristic distribution of noradrenergic terminals on the anterior horn motoneurons innervating the perineal striated muscles in the rat

SummaryDopamine-β-hydroxylase (DBH) immunohistochemistry was used to demonstrate the noradrenergic fibers and terminals in the anterior column of the rat lumbosacral spinal segments. PAP-positive varicose fibers were widely distributed in the gray matter with preferential accumulation in the nuclear regions containing motoneurons involved in the contraction of perineal striated muscles. Unmyelinated DBH fibers were composed of nodular enlargements (varicosities, 0.4–3.0 μm in diameter) and very fine, short intervals (intervaricose segments, 0.1–0.2 μm in diameter and 1.0–4.0 μm in length). DBH-positive dense products were electron microscopically often confined within small granular particles and less frequently within large granules. Additionally, in order to characterize the innervation pattern of noradrenergic fibers on dendritic bundles organized in the motoneuronal pools innervating the pelvic small muscles, semi-quantitative analysis was done in the area of the dorsolateral nucleus endowed with especially well-developed dendritic bundles. DBH terminals contacting with unreactive dendrites were more common (67.9%) than those with neuronal somata (15.1%), and the remainder (17%) had no contacts with surrounding neuronal elements. Furthermore, specialized synaptic formations were observed in only 20.1% of these nodules. The results suggest that bulbospinal descending noradrenergic neuron systems influence the functioning of pelvic muscles principally via the neuronal contacts with dendritic bundles in the spinal cord.

Fluorescence histochemical study on the noradrenergic control to the anterior column of the spinal lumbosacral segments of the rat and dog, with special reference to motoneurons innervating the perineal striated muscles (Onuf's nucleus)

SummaryThe organization of noradrenergic fibers in the lumbosacral anterior column of rats and dogs was examined in detail using a modification of a highly sensitive glyoxylic acid fluorescence histochemical method. In both rat and dog, there were greater concentrations of fluorescing noradrenergic fibers around the motoneurons innervating the perineal striated muscles (Onufs nucleus) than around other motoneuronal groups. The preferential accumulation of noradrenergic fibers in Onufs nucleus may indicate that the noradrenergic neuron system in the spinal cord of rodents and carnivores is closely related to the functional peculiarities of the perineal striated muscles, including the external anal and urethral sphincter muscles.

Distribution of serotonergic neurons in the central nervous system: a peroxidase-antiperoxidase study with anti-serotonin antibodies.

Distribution of serotonin (5-HT) neurons in the central nervous system (CNS) of various vertebrates was investigated with a highly sensitive immunohistochemical technique. Antibodies were raised in rabbits against an antigen prepared by coupling 5-HT to bovine thyroglobulin. 5-HT neurons were found to be distributed more widely and densely than has been heretofore described. Serotonergic neuronal somata are organized according to certain basic patterns, but there are interspecific differences with regard to the distribution of 5-HT fibers. The processes of 5-HT neurons form a dense plexus by ramification and anastomosis in almost all areas of the CNS, including the ventricular surfaces. In the light of our observations, Golgis reticular theory may have to be revised.

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 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.

Histochemical and electron microscopical demonstration of the sympathetic nerve fibers joining to the fourth and the sixth cranial nerves in rats

SummaryThe localization of sympathetic fibers on the floor of the cranium was studied in rats using amine fluorescence histochemistry, neuropeptide-Y (NPY) immunohistochemistry, and electron microscopy. The vast majority of amine fluorescent fibers joined the abducent nerve and were localized in the peripheral zone under the perineurium. After advancing along this nerve for some distance, the fibers diverged into many bundles that converged to form the cavernous plexus at a rostral end of the trigeminal ganglion. On the dorsal surface of the trigeminal ganglion, one or two medium-calibered fluorescent bundles ran inside or in close proximity to the trochlear nerve, while many small-calibered, brightly fluorescent bundles also extended longitudinally in the epidural connective tissue. In rats that had undergone nerve severance, NPY-immunoreactive fibers were detected at the cut ends of the abducent and trochlear nerve. The differing amounts of NPY accumulated at the rostral and the caudal stumps indicated the direction of the NPY-bcaring fibers. Electron microscopy confirmed the presence of unmyelinated fibers in both the abducent and trochlear nerves.

Immunohistochemical demonstration of serotonergic and peptidergic nerve fibers in the subcommissural organ of the dog

SummaryThe distributional patterns of serotonin-, luteinizing hormone-releasing hormone (LHRH)-, oxytocin (OXT)- and vasopressin (VP)-immunoreactive nerve fibers were studied in the subcommissural organ (SCO) of the dog by use of the peroxidase-antiperoxidase technique.Abundant serotonergic and moderate numbers of peptidergic nerve fibers running toward the ventricular surface were observed among the cylindrical ependymal cells in the SCO of the dog. Concerning the distributional density of the peptidergic nerve fibers, VP-immunoreactive fibers displayed the highest and LHRH-immunoreactive fibers the lowest values. Most serotonergic and peptidergic fibers returned to the basal portion of the SCO after forming loops immediately beneath the ventricular surface of the ependymal layer. Serotonin-immunoreactive fibers often established a perivascular plexus around the blood vessels in the SCO.At the electron-microscopic level, after use of antiserum to serotonin dark immunoprecipitate was observed in large granular vesicles and the matrix surrounding small and large, clear vesicles and mitochondria; VP immunoreactivity was localized in the large granular vesicles.Serotonergic nerve fibers could be detected in the SCO of the newborn dog. Although the distributional density was in principle not different from that in the adult animal, individual fibers showed immature features such as growth cones and insufficiently swollen varicosities. After penetrating into the ventricle, in the newborn dog, a few serotonin-immunoreactive fibers ran for a relatively long distance on the ependymal surface.