Synaptic regulation of paraventricular arginine vasopressin-containing neurons by neuropeptide Y-containing monoaminergic neurons in rats

Summary Synaptic regulation of arginine vasopressin (AVP)-containing neurons by neuropeptide Y (NPY)-containing monoaminergic neurons was demonstrated in the paraventricular nucleus of the rat hypothalamus. NPY and AVP were immunolabeled in the pre- and the post-embedding procedures, respectively, and monoaminergic fibers were marked by incorporating 5-hydroxydopamine (5-OHDA), a false neurotransmitter. The immunoreaction for NPY was expressed by diaminobenzidine (DAB) chromogen, and that for AVP by gold particles. The DAB chromogen was localized on the surface of the membrane structures, such as vesicles or mitochondria, and on the core of large cored vesicles. Gold particles were located on the core of the secretory granules within the AVP cell bodies and processes. The incorporated 5-OHDA was found as dense cores within small or large vesicular structures. From these data, three types of nerve terminals were discernible: NPY-containing monoaminergic, NPY-containing non-aminergic, and monoaminergic fibers. The AVP cell bodies appeared to have synaptic junctions formed by these nerve terminals as well as by the unlabeled nerve terminals which have small clear vesicles and large cored vesicles. These different types of nerve terminals were frequently observed in a closely apposed position on the same AVP cell bodies. The functional relationships of these three types of neuronal terminals are discussed.     

Catecholaminergic innervation of GRF-containing neurons in the rat hypothalamus revealed by electron-microscopic cytochemistry

Summary The Catecholaminergic innervation of neurons containing growth hormone-releasing factor (GRF) was examined by use of a method which combined either 5-hydroxydopamine (5-OHDA) uptake or autoradiography after intraventricular injection of ³H-noradrenaline with immunocytochemistry for GRF in the same tissue sections at the electron-microscopic level. In the ventrolateral part of the arcuate nucleus of the rat hypothalamus a large number of immunonegative axon terminals were found to make synaptic contact with GRF-like immunoreactive (GRF-LI) cell bodies and processes. ³H-noradrenaline autoradiography or 5-OHDA-labeling combined with GRF immunocytochemistry revealed that axon terminals labeled with ³H-noradrenaline or 5-OHDA make synaptic contact with the GRF-LI nerve cell bodies and processes. These findings indicate that catecholamine-containing neurons innervate GRF neurons to regulate GRF secretion via synapses in the rat arcuate nucleus.     

Immunocytochemical observations of corticotropin-releasing-factor-containing neurons in the rat hypothalamus with special reference to neuronal communication

Synapses between neurons with corticotropin-releasing-factor-(CRF)-like immunoreactivities and other immunonegative neurons in the hypothalamus of colchicine-treated rats, especially in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) were observed by immunocytochemistry using CRF antiserum. The immunoreactive nerve cell bodies and fibers were numerous in both the PVN and the SON. The CRF-containing neurons had synaptic contacts with immunonegative axon terminals containing a large number of clear synaptic vesicles alone or combined with a few dense-cored vesicles. We also found CRF-like immunoreactive axon terminals making synaptic contacts with other immunonegative neuronal cell bodies and fibers. And since some postsynaptic immunonegative neurons contained many large neurosecretory granules, they are considered to be magnocellular neurosecretory cells. These findings suggest that CRF functions as a neurotransmitter and/or modulator in addition to its function as a hormone.     

Projections to the median eminence and the arcuate nucleus with special reference to monoamine systems: Effects of lesions

The external layer of the median eminence (ELME) and the arcuate nucleus of male rats were studied with the Falck-Hillarp technique and electron microscopy of aldehyde-OsO4 or KMnO4 fixed material after various types of hypothalamic deafferentation experiments with the Haláz knife. Special reference was paid to the monoamine systems and the results can be summarized as follows. 1. The main monoaminergic input to the ELME comes from the arcuate nucleus-periventricular area via a dorsal approach. A horizontal transection through the arcuate nucleus decreases the percentage of monoamine boutons i.e. boutons with small granular vesicles, from 31.6% in the controls to 4.4% in the lesion group, whereas only a small effect is seen after anterior (or complete) deafferentations. 2. A major input to the ELME enters the basal hypothalamus at the anterior-lateral aspects (see Réthelyi and Halsáz, 1970). The fibers cut after anterior deafferentations in all probability mainly come from cell bodies localized in the anterior hypothalamus or even further rostrally but some may represent Na axons ascending from the lower brain stem. 3. The degeneration course of nerve endings in the ELME both after anterior deafferentations as well as after lesions in the arcuate nucleus is rapid (within 2-3 days) and morphologically characterized by an initial aggregation of large dence cored vesicles seemingly to electron dense bodies within the boutons and probably also to a closer spacing of the small electron lucent synaptic vesicles (see Raisman, 1972). This type of degeneration seems to take place both in monoamine and non-monoamine neurons. 4. Degenerating boutons are found in the arcuate nucleus after anterior and complete deafferentations. Thus, the anterior hypothalamus may exert an "indirect" control of the pituitary gland via synapses on arcuate neurons although quantitavely the direct influence through the projection to the ELME is of more importance. 5. After anterior deafferentations enlarged axons containing large amounts of large dense cored vesicles and other organelles are found caudally of the cut indicating the existence of rostral projections from the medial hypothalamus.     

Uptake of serotonin, 5-hydroxytryptophan and tryptophan by giant serotonin-containing neurones and other neurones in the central nervous system of the snail (Helix pomatia)

Summary Following exposure to tritiated 5-HTP, silver grains were observed over the perikarya of the GSCs (Giant serotonin cells) of Helix pomatia and other known serotonin-containing neurones in light and electron microscope autoradiograms. There was no indication that the 5-HTP was taken up by nerve endings or by non-nervous structures. The distribution of radioactivity was completely different in autoradiograms of tissue exposed to tritiated serotonin. Silver grains, often in very high concentrations, were observed only over certain fine axon branches and processes thought to be nerve endings. Electron microscope autoradiography showed that these processes contained small dense-cored vesicles, morphologically identical to those thought to sequester serotonin in the perikarya of the GSCs. The accumulation of tritiated tryptophan was less specific; all the neurone perikarya showed an accumulation of radioactivity after exposure to this substance.We are grateful to Professor J. F. Lamb for the use of the Scintillation Spectrometer.     

A radioautographic and immunocytochemical study of the GABA systems of the habenula complex in the rat

Radioautography of [³H]GABA accumulation and immunocytochemistry of glutamate decarboxylase have been used to study anatomically and morphologically the GABA system of the rat habenular (Hb) complex. Radioautographic visualisation of GABA specific neurons show a very high innervation of the complex including both stria medullaris (SM), the habenular commissure and the periventricular thalamic fibers (FPVT). A massive labeled fiber system in the SM appears to divide into two branches when it reaches the Hb nuclei: a part of fibers continue their course dorsally to the nuclei up to the habenular commissure; other fibers enter the Hb lateralis or run along the ventral Hb medialis at the level of FPVT. The staining is markedly diminished in the entire complex in response to SM lesions. In the Hb lateralis, the radioautographic-positive reaction is mainly bound to labeled fibers or axonal varicosities. However GAD immunocytochemistry reveals some GAD-positive cell bodies in the ventro-median portion of the nucleus. In the Hb medialis the radioautographic and immunocytochemical staining is observed in the neuropile between the unlabeled large cell bodies. In the subependymal layer bundles of processes are strongly labeled and form a continual strain behind the unlabeled ependymocytes. Three types of reactive terminals have been differentiated based on size and shape of vesicles. Some of them are exclusively characterized by clear round vesicles and probably have their origin in the septum. Others contain clear vesicles and some large dense-cored vesicles and disappear after mesencephalic Raphe lesions or 5,7-dihydroxytryptamine treatment. They could correspond to terminals of raphe neurons with a double potentiality GABA and 5HT. The last exhibit mainly a dense population of large dark-cored granules similar to the ones found in neurosecretory nerve endings. However numerous fibers morphologically similar to the reactive fibers are unlabeled.     

Electron microscopic examination of the orexin immunoreactivity in the dorsal raphe nucleus

The ultrastructure and the synaptic relationships of the orexin-A-like immunoreactive fibers in the dorsal raphe nucleus were examined with an immunoelectron microscopic method. At the electron microscopic level, most of the immunoreactive fibers, a varicosity appearance at the light microscopic level, were found as axon terminals. The large dense-cored vesicles contained in the immunoreactive axon terminals were the most intensely immunostained organellae. These axon terminals were often found to make synapses. While the axo-dendritic synapses were usually asymmetric in appearance, the axo-somatic synapses were symmetric. Orexin-A-like immunoreactive processes with no synaptic vesicles were also found. These processes often received asymmetric synapses. With less frequency, the synapses were found between the orexin-like immunoreactive processes. The results suggest that the orexin peptides are stored in the large dense-cored vesicles; the orexin-containing fibers may have influences on the physiological activities of the dorsal raphe nucleus through direct synaptic relationships.     

Axons containing neuropeptide Y innervate arginine vasopressin-containing neurons in the rat paraventricular nucleus

Summary Synaptic connections between neurons immunoreactive for arginine vasopressin (AVP) and axon terminals immunoreactive for neuropeptide Y (NPY) were found in the magnocellular part of the paraventricular nucleus (PVN) in the rat hypothalamus. In pre-embedding double immunolabeling, NPY axon terminals labeled with diamin-obenzidine (DAB) reaction product established synaptic junctions on the perikarya and neuronal processes of AVP neurons labeled with silver-gold particles. Ultrastructural morphology of the neurons was more suitably preserved by a combination of pre- and post-embedding procedures. The presynaptic NPY terminals contained many small clear vesicles and a few cored vesicles, and DAB chromogen (immunoreaction product) was located on the surface of the vesicular profiles and on the core. The postsynaptic AVP neurons possessed many large secretory granules labeled with gold particles. At the synaptic junctions, small clear vesicles were accumulated at the presynaptic membrane, and the postsynaptic membrane was coated with a dense accumulation of fine electron dense particles. The perikarya also received synapses made by immuno-negative axon terminals containing many small clear vesicles and a few cored vesicles. These terminals were found more frequently than those containing NPY.     

Axons containing neuropeptide Y innervate arginine vasopressin-containing neurons in the rat paraventricular nucleus. Dual electron microscopic immunolabeling

Synaptic connections between neurons immunoreactive for arginine vasopressin (AVP) and axon terminals immunoreactive for neuropeptide Y (NPY) were found in the magnocellular part of the paraventricular nucleus (PVN) in the rat hypothalamus. In pre-embedding double immunolabeling, NPY axon terminals labeled with diaminobenzidine (DAB) reaction product established synaptic junctions on the perikarya and neuronal processes of AVP neurons labeled with silver-gold particles. Ultrastructural morphology of the neurons was more suitably preserved by a combination of pre- and post-embedding procedures. The presynaptic NPY terminals contained many small clear vesicles and a few cored vesicles, and DAB chromogen (immunoreaction product) was located on the surface of the vesicular profiles and on the core. The postsynaptic AVP neurons possessed many large secretory granules labeled with gold particles. At the synaptic junctions, small clear vesicles were accumulated at the presynaptic membrane, and the postsynaptic membrane was coated with a dense accumulation of fine electron dense particles. The perikarya also received synapses made by immuno-negative axon terminals containing many small clear vesicles and a few cored vesicles. These terminals were found more frequently than those containing NPY.     

Neuroglandular synapses in the pharynx of the sea anemone Aiptasia pallida (Cnidaria, Anthozoa)

Scanning and transmission electron microscopy of the pharynx of the sea anemone Aiptasia pallida revealed a heavily ciliated epidermis and two types of gland cells not known previously to be innervated. By tracing serial cross sections of the pharynx, we located and characterized two types of neuroglandular synapses (i.e., those having clear vesicles and those with dense-cored vesicles). The diameters of the vesicles at each synapse were averaged; clear vesicles ranged from 70 to 103 nm in diameter and were observed at synapses to both mucous and zymogenic gland cells. Dense-cored vesicles ranged from 53 to 85 nm in diameter and were observed at synapses to two mucous gland cells. One mucous gland cell had three neuroglandular synapses, one with clear vesicles and two with dense-cored vesicles. The occurrence of either clear or dense-cored vesicles at neuroglandular synapses suggests that at least two types of neurotransmitter substances control the secretion of mucus in the sea anemone pharynx. To date, only clear vesicles have been observed at a neurozymogenic gland cell synapse in the pharynx. No evidence of immunoreactivity to phenylethanolamine-N-methyl transferase was observed at neuroglandular synapses, suggesting that adrenaline is not a transmitter in the pharynx of A. pallida.     

Fine structure of nervous elements in the pancreas of some vertebrates

Summary The innervations of the exocrine and endocrine pancreas of some vertebrate animals were studied by electron microscopy. The pancreas of the bat and monkey contained ganglion cells in the interlobular connective tissue or between acinar cells. Unmyelinated nerve fibers ran through the interlobular connective tissue and reached the exocrine and endocrine parts, and terminated there as the endings. The nerve endings within the pancreas could be divided into four types: 1. Type 1-a of the nerve ending contained only agranular synaptic vesicles of about 500 Å in diameter. 2. Type 1-b characterized by containing agranular synaptic vesicles and some large cored vesicles (1,000 Å diameter). These two types of nerve endings might belong to the cholinergic (parasympathetic) endings. 3. Type 2-a contained small cored vesicles and agranular synaptic vesicles along with a few large cored vesicles. 4. Type 2-b was characterized by containing vesicles of the same size as those of agranular synaptic vesicles, and a majority of these vesicles contained bar-shaped crystalloids. This ending also contained a few large cored vesicles. These nerve endings of Type 2-a and 2-b might be the adrenergic (sympathetic) endings.     

Ultrastructure of neurons in the ventromedial nucleus or the hypothalamus in ovariectomized rats with or without estrogen treatment

Summary The fine structure of the ventrolateral and dorsomedial subdivisions of the ventromedial nucleus (VMN) of the hypothalamus was examined in ovariectomized/control and ovariectomized/estrogen-treated rats to compare neurons of these areas to other neurons (specifically the ventrolateral thalamus), and to determine the effects of estrogen on these cells. The neurons of the VMN contain a large nucleus with a prominent nucleolus, rough endoplasmic reticulum (RER), polysomes, a Golgi complex, coated, uncoated and dense-cored vesicles, lysosome-like bodies, inclusion bodies, multivesicular bodies, whorl bodies and myelin figures. Similar organelles were present in the neurons of the ventrolateral thalamus, although polysomes were more prominent, and the cells lacked dense-cored vesicles in the perikarya. Differences in the cells of the VMN between ovariectomized/control and ovariectomized/estrogen-treated rats included a more conspicuous stacking of the RER and greater number of dense-cored vesicles in the estrogen-treated group in both the ventrolateral and dorsomedial subdivisions. In both areas the differences were statistically significant, although more marked in the ventrolateral subdivision. In both VMN subdivisions, the increased stacking of the RER could be correlated with the greater number of dense-cored vesicles and may reflect increased biosynthesis of a secretory product.Supported by grants from the National Institutes of Health (1 R01 NS15889-01) to R.S.C. and (HD-05751) to D.W.P.     

Morphology of the cat auditory cortex

The ultrastructural features of the primary auditory cortex of the cats and the character of the endings of geniculo-cortical afferent fibers in the early stages of experimental degeneration evoked by destruction of the medial geniculate body were studied. In all layers of the cortex asymmetrical synapses with round synaptic vesicles on dendritic spines and on thin dendritic branches of pyramidal and nonpyramidal neurons are predominant. Symmetrical synapses with flattened or polymorphic vesicles are distributed chiefly on the bodies of the neurons and their large dendrites. Because there are few symmetrical synapses which could be regarded as inhibitory it is postulated that inhibitory influences may also be transmitted through asymmetrical synapses with round vesicles. Other types of contacts between the bodies of neurons, dendrites, and glial processes also were found in the auditory cortex. Degenerating terminals of geniculo-cortical fibers were shown to terminate chiefly in layer IV of the cortex on pyramidal and nonpyramidal neurons. Degeneration was of the dark type in asymmetrical synapses with round vesicles. The results are dicussed in connection with electrophysiological investigations of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 519–524, September–October, 1973.     

Electron-microscopic cytochemistry of the catecholaminergic innervation of ACTH-containing neurons in the rat hypothalamic arcuate nucleus

The synaptic relationship between catecholamine terminals and adrenocorticotropic hormone (ACTH)-containing neurons in the arcuate nucleus (AN) of the rat hypothalamus was investigated by electron microscopy, using ACTH immunocytochemistry combined with autoradiography after 3H-dopamine (3H-DA) injection or 5-hydroxydopamine (5-OHDA) uptake in the same tissue section. ACTH-like (ACTH-LI) immunoreactive nerve cell bodies and fibers received synaptic inputs by axon terminals labeled with 3H-DA or 5-OHDA in the AN. This suggests that catecholaminergic neurons, at least DA- and 5-OHDA-containing neurons, may play an important role in the regulation of ACTH secretion or other functions of ACTH neurons via synapses in the AN of the rat hypothalamus.     

Colchicine effects on neurosecretory neurons and other hypothalamic and hypophysial cells,with special reference to changes in the cytoplasmic membranes

Summary The morphological effects of colchicine on the entire neurosecretory (NS) tract and on various hypothalamic nuclei have been studied. The perturbation in axonal flow, indicated by the accumulation of NS material, coincide with fragmentation of the cytoplasmic membranes, i. e. the Golgi apparatus and the endoplasmic reticulum, whereas the neurotubules remain relatively well preserved. Autophagic destruction of NS material is observed along the entire length of the NS fibres. The rapid and systematic changes in the axoplasmic reticulum, known to store calcium, lead us to envisage a role for this system — similar to that of the sarcoplasmic reticulum — in controlling the transport of NS vesicles. The junctional zone between the stalk and the neural lobe seems to play a particular rôle in the transport of NS material to the posthypophysial terminals of the NS axons. Colchicine provokes an increase in dense-cored vesicles in most of the neurons of the other hypothalamic nuclei studied: arcuate, suprachiasmatic, periventricular and ventromedial. Membranous alterations are also observed in these sites. Colchicine administered to animals which were hypothyroid, castrated or adrenalectomized, reveals stimulated neurons, identified by their excessive content of dense-cored vesicles. These neurons display no specific localization, for they occur in all hypothalamic nuclei, irrespective of the stimulation. The frequency of stimulation of neurons of the periventricular nucleus is striking.     

The fine structure of the hypothalamic secretory neurons of the White-crowned Sparrow,Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae)

Summary The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy.The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and densecored granules 1,500–2,200 Å in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800–1,000 Å in diameter and clear vesicles 500 Å in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region.The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 Å in diameter. The profiles of axons within the neuropil contain dense-cored granules 800–1,000 Å in diameter and clear vesicles 500 Å in diameter.The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 Å in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya.Occasionally, neurons with granules 1,500–2,200 Å in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system.The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 Å in diameter.This investigation was supported by Grant No. 5R040 Japan-U.S. Cooperative Science Program of the Japan Society for the Promotion of Science to Professor H. Kobayashi and Professor S.-I. Mikami, by a Scientific Research Grant No. 56019 from the Ministry of Education of Japan to S.-I. Mikami, by support from the Deutsche Forschungsgemeinschaft (Schwerpunktprogramm Biologie der Zeitmessung) to Prof. A. Oksche and by Grant No. GF 33334, U.S.-Japan Cooperative Science Program of the National Science Foundation to Prof. D.S. Farner.Herrn Professor Dr. Dres h.c. Wolfgang Bargmann zu seinem 70. Geburtstag am 27. Januar 1976 gewidmet.     

CHARACTERIZATION OF AN UNUSUAL CATECHOLAMINE-CONTAINING CELL TYPE IN THE TOAD HYPOTHALAMUS : A Correlated Ultrastructural and Fluorescence Histochemical Study

A nucleus of catecholamine-containing cells bordering the preoptic recess of the toad hypothalamus has been studied by both fluorescence histochemical and electron microscopic methods. The perikarya of these cells form one to three rows immediately subjacent to the ependyma. They send brightly fluorescent apical processes between the ependymal cells to the ventricular surface, and also give rise to long basal processes, the proximal portions of which are also fluorescent. These cells contain two distinctive constitutents: juxtanuclear bundles of tightly packed filaments, the members of which are separated from one another by only ~100 A, and large numbers of dense-cored vesicles (400–2200 A in diameter), which appear to arise from an agranular tubular reticulum distinct from the Golgi apparatus. Axons containing either clear vesicles alone or clear and dense-cored vesicles form synapses on the subependymal cells, but no evidence has been found that the subependymal cells themselves form presynaptic contacts, or that axons originate from them. The cytological characteristics of these catecholamine-containing cells, plus the fact that they border directly on the cerebrospinal fluid, suggest that they may be more closely related to peripheral chromaffin cells than to the other cell types intrinsic to the central nervous system, and the name "encephalo-chromaffin cells" is therefore proposed for them. The possible functions of such cells in the central nervous system are discussed.     

Electron microscopic observations on synapse-like contacts between pituicytes and different types of nerve fibers in the anuran pars nervosa

Summary Pituicytes of Rana pipiens could be classified into two types, pale and dense, according to their relative densities of cytoplasm and the populations of free ribosomes and cell organelles. An intermediate type of pituicyte was also recognized.Lipid droplet such as are typical in the cytoplasm of mammalian pituicytes, are not in the cytoplasm of either types of frog pituicyte. Both types have long cytoplasmic processes which run among the nerve fibers, and some of them end at the pericapillary space.Nerve endings making synapse-like contacts with the cell bodies or the processes of the pituicyte are frequent. According to the structures and sizes of granules and vesicles in the nerve endings, these endings are classified into one of three types: 1) A, which appears to be a peptidergic neuronal ending containing dense granules 1,200–2,000 Å in diameter and small clear vesicles 300–400 Å in diameter; 2) B, which appear to be monoaminergic endings containing cored vesicles 600–1,000 Å in diameter and small clear vesicles 300–500 Å in diameter; 3) C, which appear to be cholinergic endings containing only small clear vesicles. Type C endings are relatively rare. In the synaptic area the axonal membranes appose those of the pituicytes across a gap of about 200 Å and numerous presynaptic vesicles are clustered or accumulated near the presynaptic membranes.The author wish to express his hearty thanks Professor Dr. A. Gorbman, Zoology Department, University of Washington, Seattle, U.S.A. and Professor Dr. H. Fujita for their helpful advices and criticisms. The frog tissues were obtained and fixed in Professor A. Gorbman's laboratory supported by U.S.P.H.S. grant NS 04887.     

Ultrastructural localization of RFamide-like peptides in neuronal dense-cored vesicles in the peduncle of Hydra

The presence of Arg-Phe-amide (RFamide)-like peptides in dense-cored vesicles in neurons of the peduncle of Hydra was demonstrated by immunogold electron microscopy. Thin sections of Lowicryl-embedded tissue labeled with antisera to RFamide and 5-nm gold-conjugated, secondary antibody and of Epon-Araldite-embedded tissue labeled with 15-nm gold particles revealed a concentration of RFamide-like immunoreactivity over the granular cores of vesicles in epidermal ganglion cells. Gold-labeled, dense-cored vesicles were present in the perikaryon, long thin neurites, and axon terminals of these neurons. The aggregation of labeled dense-cored vesicles in an axon terminal on the myoneme of an epitheliomuscular cell suggests a possible function of RFamide-like peptides in neuromuscular transmission. Gold staining of dense-cored vesicles completely disappeared when the RFamide antiserum was preabsorbed with 10 micrograms/ml RFamide. These results are the first demonstration that the dense-cored vesicles of Hydra neurons contain a neuropeptide.     

Localization of neuropeptide Y in human sympathetic ganglia: Correlation with met-enkephalin, tyrosine hydroxylase and acetylcholinesterase

Summary The relationships of immunoreactive neuropeptide Y, enkephalin and tyrosine hydroxylase, on the one hand, and acetylcholinesterase histochemical activity, on the other, were studied in human lumbar sympathetic ganglia. Two thirds of the ganglion cells contained immunoreactive neuropeptide Y. Electron microscopically the immunoreaction was localized in the Golgi apparatus and in large dense-cored vesicles in the nerve endings. Most of the neuropeptide-containing neurons and nerve fibres were also reactive for tyrosine hydroxylase. Nerve fibres reactive for neuropeptide Y were found around ganglion cells regardless of their transmitter contents, whereas enkephalin-reactive nerve terminals surrounded only acetylcholinesterase-containing neurons. The results demonstrate that neuropeptide Y is colocalized with noradrenaline in most of the human sympathetic neurons and that the nerve fibres may innervate selectively the noradrenergic and cholinergic subpopulations of ganglion cells depending on the transmitters of the nerves.