Cs. Léránth

Serotoninergic endings on VIP-neurons in the suprachiasmatic nucleus and on ACTH-neurons in the arcuate nucleus of the rat hypothalamus. A combination of high resolution autoradiography and electron microscopic immunocytochemistry

A combination of immunocytochemistry with transmitter specific autoradiography at the electron microscopic level was used to identify vasoactive intestinal polypeptide (VIP)- or ACTH-containing neurons and serotoninergic nerve terminals in the suprachiasmatic (SCN) and arcuate nuclei (AN). We observed nerve terminals showing selective uptake of [3H]serotonin forming synaptic contact with perikarya or dendrites where the postsynaptic structures exhibited VIP-like immunoreactivity in the SCN and ACTH-like immunoreactivity in the AN. The findings provide ultrastructural evidence that serotoninergic nerve fibers terminate on VIP-neurons in the SCN and on ACTH-neurons in the AN.

Commissural afferents innervate glutamate decarboxylase immunoreactive non-pyramidal neurons in the guinea pig hippocampus.

Abstract The innervation of GABAergic hippocampal neurons by commissual fibers was investigated in the guinea pig by a combined anterograde degeneration - immunocytochemical technique. Presumed GABAergic neurons were identified by immunocytochemistry for glutamate decarboxylase (GAD) and the commissural fibers by electron-dense degeneration following contralateral transection of the fimbria. Commissural afferents were found to establish asymmetric synaptic contacts with non-pyramidal GAD-immunoreactive neurons located in subpyramidal and suprapyramidal zones of region CA1. The observed connection suggests that inhibition of pyramidal cells may occur in a feed-forward manner as postulated by electrophysiological studies.

Synaptology and sources of vasoactive intestinal polypeptide and substance p containing axons of the cat celiac ganglion. An experimental electron microscopic immunohistochemical study

We have examined the possible origin of vasoactive intestinal polypeptide (VIP) and substance P-containing axons and the synapses formed by these axons in the celiac ganglion of the cat, by means of ultrastructural immunohistochemistry combined with various surgical lesions. Axons containing VIP as well as those immunopositive for substance P, formed axo-dendritic and axosomatic synapses with principal ganglion cells. After transection of the superior mesenteric nerve numerous degenerated axonal profiles could be found in the celiac ganglion. Some of these contained VIP immunoreactivity. By contrast in alternate sections stained with substance P antibody only intact axons were labelled. Bilateral vagotomy resulted in the appearance of degenerating axonal profiles in the celiac ganglion, some of which could be stained with substance P antiserum but not with VIP antiserum. Following removal of dorsal root ganglia (Th6-Th12) from both sides, a large number of degenerated axons were found, many of which were immunopositive for substance P but not for VIP. We conclude that the peripheral input to the celiac ganglion contains VIP fibers which form synapses with principal ganglion cells. Substance P-containing fibers reach the celiac ganglion via the vagal nerve as well as from the dorsal root ganglia, and they form synapses with the principal ganglion cells. It is proposed that the VIP and the substance P-containing axons are involved in two different peripheral reflex loops.

Morphological and biochemical changes in the rat interpeduncular nucleus following the transection of the habenulo-interpeduncular tract

Chol ine acetyl t ransferase (ChAC) is responsible for the synthesis o f acetylcholine. Accord ing to Palkovi t s et al. ~ the C h A C level is the highest in the interpeduncu la r nucleus (NIP) o f the m a m m a l i a n brain. Af te r t ransec t ion o f the habenu loin te rpeduncu la r t rac t C h A C decreases to a few per cent o f the original leveF, 3. The present work aims at the ident i f icat ion o f the morpho log ica l correlates o f the b iochemical changes fol lowing habenu lo in t e rpeduncu la r t rac t lesions. The morpho log ica l cha rac te r i za t ion o f a typical chol inergic synapse was also a t tempted . Ra ts o f bo th sexes (150-200 g) were used. F o u r animals served as controls. Uni la te ra l e lectrolyt ic lesions o f the habenu la were pe r fo rmed on 12 rats (Fig. 4) and bi la tera l lesions o f the habenu la or the habenu lo in te rpeduncu la r t ract were carr ied out on an add i t iona l 12 animals. Both groups were sacrificed af ter 2, 4, and 7 days and p repa red par t ly for l ight mic roscopy with the F i n k H e i m e r me thod and par t ly for e lec t ron microscopic study. The exper imenta l and cont ro l an imals were perfused with K a r n o v s k y solut ion and embedded into D u r c u p a n for e lec t ron microscopical investiga t ions and examined with a Jeol 100B electron microscope. In ano the r group t 12 rats) o f b i la tera l habenu la r les ioned animals , the in te rpeduncula r nuclei were removed by punching out pellets f rom 300 # m th ick frozen sections 5 3 weeks af ter opera t ion . The dorsa l and ventral pa r t o f the nuclei were taken out separately. Chol ine acetyl t ransferase act ivi ty was assayed by a modif ica t ion o f the method o f Bull and OderfeldN o w a k 1, pro te in was de te rmined accord ing to the me thod o f Lowry et a l / a n d the results were expressed as pmoles p roduc t fo rmed (/zg protein/h) .

Commissural afferents to the rat hippocampus terminate on vasoactive intestinal polypeptide-like immunoreactive non-pyramidal neurons. An EM immunocytochemical degeneration study

In the rat hippocampus, bipolar non-pyramidal neurons in stratum radiatum and stratum oriens and multipolar neurons in stratum lacunosum-moleculare react for vasoactive intestinal polypeptide (VIP) immunostaining, but pyramidal cells do not. Such bipolar VIP-like immunoreactive neurons in strata radiatum and oriens of regio superior were studied by electron microscopy for synaptic contacts with commissural afferents. The commissural fibers were identified by their anterograde degeneration induced by contralateral fimbria transections 2 days before sacrifice. Electron-dense degenerated boutons of commissural origin were found in synaptic contact with the cell bodies and dendrites of the VIP-like immunoreactive non-pyramidal cells.

Depletion of substance P and somatostatin in the upper dorsal horn after blockade of axoplasmic transport

SummaryIn the upper dorsal horn of the rat lumbosacral spinal cord, substance P and somatostatin are present in two distinct and different populations of primary central afferent terminals. Substance-P-positive terminals are mainly concentrated in lamina I, while somatostatin-positive terminals are confined to lamina II. Although these two populations of primary afferent terminals differ at light- and electron-microscopic level, they are equally affected by transganglionic degenerative atrophy (TDA) which is induced by the blockade of axoplasmic transport in the segmentally related, ipsilateral sensory nerve by the local application of Vinblastin, a microtubule inhibitor. In consequence, substance P and somatostatin are depleted in the medial and intermediate portions of the upper dorsal horn, while the lateralmost area, which represents the postaxial portion of the dermatome, remains virtually intact. Substance P and somatostatin in propriospinal elements and the axonal meshwork within the dorsolateral funicle are not affected by TDA. Neurotensine, a propriospinal neuropeptide, does not show any alterations in the affected spinal segments.

Distribution of vasoactive intestinal peptide (VIP) following various brain transections in the rat by radioimmunoassay and electronmicroscopic immunocytochemistry

Abstract Highest concentrations of vasoactive intestinal peptide (VIP) are found in the rat cerebral cortex and hypothalamic suprachiasmatic nucleus (SCN), located by electronmicroscopic immunocytochemistry in cell bodies, dendrites and nerve terminals. The unchanged level of VIP in the parietal cortex after transection of the corpus callosum supports our former observation that VIP in the cerebral cortex is present in short intrinsic neurons. A similar conclusion can be drawn for the dorsal hippocampus after superior fornix transection. The high VIP level in the SCN is depleted by periventricular transection immediately caudal to the nucleus, indicating that VIP fibers or neuronal inputs necessary for VIP synthesis in the SCN have been lesioned. These neuronal inputs do not seem to be of serotonin origin, since medial forebrain bundle lesion does not alter VIP concentrations in the SCN. Even if a high number of VIP-containing cell bodies are present in the SCN, it does not seem that VIP fibers from this nucleus project to the median eminence directly via a periventricular path or through the retrochiasmatic area.

Light and electron microscopic immunocytochemical localization of vasoactive intestinal polypeptide VIP-like activity in the rat small intestine

Vasoactive intestinal polypeptide nerve processes and cell bodies were identified by electron microscopic immunocytochemistry in the rat small intestine. Labeled nerve processes were numerous in the inner circular smooth muscle coat and mainly in the mucosa, but were absent in the longitudinal muscle layer. Submucosal blood vessels were often surrounded by immunoreactive vasoactive intestinal polypeptide positive nerves, in close associations (distance less than 40 mn) to blood vessel basement membranes and to smooth muscle cells. In the ganglia of the myenteric and submucous plexuses, labeled fibers surrounded unstained neural cell bodies. The synaptic vesicles of vasoactive intestinal polypeptide positive terminals were 35-40 nm in diameter and some dense core vesicles (80-120 nm in diameter) were also observed in the same profiles. These observations suggest that vasoactive intestinal polypeptide nerves may participate in regulating smooth muscle activity and local blood flow in the small intestine.

Termination in the prevertebral abdominal sympathetic ganglia of axons arising from the local (terminal) vegetative plexus of visceral organs

SummaryDegeneration of synaptic axon terminals in the prevertebral (celiac and superior mesenteric) ganglia, occurring after operative interferences on visceral organs, shows that processes of ganglion cells (probably of Dogiel type II) located in the terminal ganglia of the gallbladder and the small intestine reach and establish synapses in the prevertebral ganglia. This finding is in accordance with the persistence of delicate axons in the peripheral stumps of visceral nerves two weeks after removal of the celiac ganglion. These results speak in favour of the existence of peripheral reflex arcs in the vegetative nervous system.

Axon types of prevertebral ganglia and the peripheral autonomic reflex arc

Prevertebral ganglia of cats and rats were studied by means of electron microscopy. Ganglia from control unoperated animals were compared with others following experimental interruptions of postganglionic and preganglionic afferent pathways. Elaborate interconnections were found between peripheral ganglia and visceral organs forming peripherally closed neuronal circuits. Three types of axons were distinguished as main constituents. On this morphological basis the existence of two kinds of peripheral reflex arcs has been postulated.