Reiji Kishida

THE SPINAL SYMPATHETIC PREGANGLIONIC CELL COLUMN IN THE PUFFER FISH, TAKIFUGU NIPHOBLES

Abstract.Little is known about the spinal sympathetic organization in teleosts. We examined the location of the sympathetic preganglionic neurons with horseradish peroxidase (HRP) labeling. After HRP application to the sympathetic trunk or celiac ganglion, labeled neurons were found just dorsal – dorsolateral to the central canal. They form a cell column (central autonomic nucleus) at the level of the posterior rootlet of the first spinal nerve to the third spinal nerve. HRP application to the sympathetic trunk produced labeling in almost the entire central autonomic nucleus, but HRP application to the celiac ganglion produced labeling in only the rostral half of the central autonomic nucleus. These results suggest that there is some topographical arrangement in the rostrocaudal part of the central autonomic nucleus. On the other hand, the fact that the sympathetic preganglionic neurons are within a single cell column and have no mediolateral segregation means that the target-related or function-associated mediolateral arrangement found in tetrapods is lacking in this species. We also found some labeling in the central autonomic nucleus after HRP application to the cranial nerves. This may indicate that the preganglionic neurons project to the cranial nerves.

NADPH-diaphorase activity in the sympathetic preganglionic neurons of the filefish, Stephanolepis cirrhifer.

Enzyme histochemistry combined with horseradish peroxidase retrograde tracing demonstrated NADPH-diaphorase activity in the spinal sympathetic preganglionic neurons in the spinal cord of the filefish, Stephanolepis cirrhifer, these neurons with NADPH-diaphorase activity were located just dorsal and lateral to the central canal. The results indicate that nitric oxide is synthesized in the spinal sympathetic preganglionic neurons of filefish.

Coexistence of galanin and substance P in the mouse nasal mucosa, including the vomeronasal organ.

Immunohistochemical fluorescent double labeling revealed the coexistence of galanin and substance P in nerve fibers in the mouse nasal mucosa. At the base of and in the epithelium, all galanin fibers also contained substance P, but around the blood vessels and glands, most of them did not. Since substance P fibers in the nasal mucosa originate from the trigeminal ganglion, these results suggest that galanin fibers in the submucosal region originate from ganglia other than the trigeminal.

Visual and infrared input to the same dendrite in the tectum opticum of the python, python regius: electron-microscopic evidence

In snakes with infrared receptors, the optic tectum receives input from both the visual and the infrared senses. We investigated the infrared and optic fiber terminations in the tectum with a combination of horseradish peroxidase and degeneration labeling. In addition to synapses by visual and infrared fibers onto individual neurons, we were able to observe for the first time visual and infrared synapses on one and the same dendrite.

Nerve fibers immunoreactive for substance P and calcitonin gene-related peptide in the cervical spinal ventral roots of the mouse

We demonstrate the existence of nerve fibers possessing substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity in the mouse cervical ventral roots. The distribution of the SP and CGRP fibers was similar, but CGRP fibers were generally more numerous. Both types entered the ventral pia mater or formed hairpin loops, but they did not enter the spinal cord directly through these roots. SP and CGRP fibers in the ventral roots were thin and had many varicosities. We suggest that these SP and CGRP fibers are involved not only in a sensory mechanism, but also in other functions, via the release of SP and CGRP from varicosities in the ventral roots.

Direct projections from the spinal cord to the trigeminal sympathetic ganglion of the puffer fish, Takifugu niphobles

The sympathetic trunk of teleosts extends into the cranial levels, forming the cranial sympathetic ganglia. When horseradish peroxidase was applied to the trigeminal sympathetic ganglion (a sympathetic ganglion at the level of the trigeminal nerve) of the puffer fish, Takifugu niphobles, retrogradely labeled neurons were found in the central autonomic nucleus (a distinct cell column in the rostral part of the spinal cord). The central autonomic nucleus has been known to contain preganglionic neurons projecting to the sympathetic ganglia at the spinal levels. Thus, the present results indicate that the central autonomic nucleus in the spinal cord of teleosts contains not only preganglionic neurons projecting to the sympathetic ganglia at the spinal levels, but also neurons projecting to the sympathetic ganglia at the cranial levels.

Development of substance P immunoreactivity in the mouse vomeronasal organ

We investigated the development of substance P immunoreactivity in mouse vomeronasal organs in embryos, juveniles, and adults. In all stages, substance P fibers were found in the receptor-free epithelial area, but never in the neuroepithelium. Substance P fibers were found sparsely in the lamina propria of 15-day-old embryos. Although buds of the vomeronasal glands in the cavernous tissue were observed in 17-day-old embryos, and gradually grew in size and numbers, the substance P fibers around them decreased after about the 13th day. Thus, substance P may be a trophic factor for the development of the vomeronasal glands in the cavernous tissue. We first recognized substance P fibers reaching the surface of the receptor-free epithelium in 13-day-old pups. In 21-day-old mice, substance P fibers were as well developed as in adult mice. Considering the development of the substance P fibers in the receptor-free epithelium and the cavernous tissue, they probably cause the vasodilation of the cavernous tissue via local axon reflexes. These structures may then act as a defense system, eliminating noxious stimulus substances sucked into the vomeronasal organ.

Somatosensory and visual correlation in the optic tectum of a python, Python regius: a horseradish peroxidase and Golgi study

In snakes with infrared receptors the optic tectum receives infrared input in addition to visual and general somatosensory inputs. In order to observe their tectal termination patterns in ball pythons, Python regius, we injected horseradish peroxidase (HRP) into the nucleus of the lateral descending trigeminal tract (LTTD) which mediates infrared information, the optic nerve, and the nucleus of the trigeminal descending tract (TTD) which relays general somatosensory information. Fibers from LTTD were found in layers 5-13 of the contralateral optic tectum, and were especially dense in layers 7a-8. Optic nerve fibers terminated in layers 7a-13 of the contralateral tectum, and mainly in layers 12-13. TTD fibers were few, and could be seen in only the rostral half of the contralateral tectum. These fibers were found in layers 5-7b, but mainly in layers 6-7a. Among various types of neurons stained by the Golgi-Cox method, we focused on six types of neurons whose dendritic arborization overlapped with the distribution of the terminals of these sensory afferents described above. It is possible that these different sensory modalities converge on a single neuron of the various types.

Enhancement of serotonergic immunoreactivity in sympathetic cerebrovascular nerve fibers after experimental embolic stroke

We examined 5-hydroxytryptamine-like immunoreactive cerebrovascular nerve fibers in rats after experimental thromboembolic stroke. Although there were no visible 5-hydroxytryptamine-like immunoreactive nerve fibers in normal animals, we found many of these fibers near the clot emboli 30 min after the stroke, and the number of fibers increased slightly with time. In immunohistochemical double staining, these fibers corresponded to neuropeptide Y-like immunoreactive nerve fibers. And they were not observed in animals after superior cervical ganglionectomy. These findings suggest that the sympathetic nerves take up serotonin released from intraluminal aggregating platelets.

Ultrastructural studies on the giant terminals in the dorsal octavolateralis nucleus of lampreys

The dorsal octavolateralis nucleus of lampreys is a primary nucleus for electroreceptive stimuli in the medulla. In Lampetra japonica, the rostral and caudal thirds of this nucleus are exclusively occupied by giant terminals, which become evident when the primary fibers of an electrosensory nerve (recurrent branch of the anterior lateral line nerve) are labeled with horseradish peroxidase. We studied the ultrastructure of these terminals. They contain neurofilaments, mitochondria, microtubules, and tubular membranous structures. Many synapses, all of the chemical type, are located around the neck region of the terminal swellings. Many vesicular structures, which are clear, round, and uniform in size, and most of which are probably synaptic vesicles, are densely clustered in a single large mass in the neck region of the terminals. Some of the tubular structures may serve as a membrane reservoir for the large number of synaptic vesicles required in the giant terminals.