Localization of noradrenaline and serotonin in nerves in the pineal gland of rats and guinea-pigs studied by glyoxylic acid histofluorescence and electron microscopy

Summary The nerves in the pineal gland of the rat and guinea-pig contain both noradrenaline and serotonin and fluoresce intensely after histofluorescence procedures. Vesicle-filled terminals in the perivascular space of the pineal body contain numerous clear and dense-cored vesicles. A 5mg/kg dose of reserpine causes disappearance of histofluorescence from the pineal nerves and a virtual elimination of dense-cored vesicles from vesicle-filled terminals. A 1mg/kg dose of reserpine results in loss of fluorescence and virtual depletion of dense cores in nerves in the rat, but the guinea-pig pineal nerves continue to fluoresce lightly and the dense-cored vesicles are still present but reduced to about 1/3 in number. Subsequent treatment of lightly reserpinized guinea-pigs withp-chlorophenylalanine, a specific depletor of serotonin, results in dis ppearance of fluorescence in nerves in the pineal gland and virtual depletion of the remaining dense cores. A dose of 1mg/kg reserpine succeeds in depleting noradrenaline from most peripheral nervous structures of the guinea-pig. Hence, the remaining monoamine in guinea-pig pineal nerves after depletion of noradrenaline appears to be serotonin located in the remaining dense-cored vesicles. Since, in lightly reserpinized guinea-pig pineal nerves, a number of dense-cored vesicles containing serotonin are still present after depletion of noradrenaline, it is suggested that noradrenaline and serotonin are not in the same vesicles at the same time.     

Structure and innervation of the pineal gland of the rabbit,Oryctolagus cuniculus (L.)

In the rabbit pineal gland two types of postganglionic nerve endings were found which are characterized by the presence of small dense-core vesicles or small clear vesicles. Pharmacological and cytochemical experiments showed then to be noradrenergic and cholinergic, respectively. Both types were often present in the same nerve bundle, occasionally in close opposition. Intrapineal neurons were only rarely observed. They showed cholinergic synapses on their perikaryon and dendrites as well as noradrenergic axo-dendritic close contacts. Bilateral extirpation of the superior cervical ganglia revealed the postganglionic sympathetic origin of the pineal noradrenergic nerve fibres. Moreover, it appeared that these ganglia are hardly, if at all, involved in the pathway of pineal cholinergic innervation. The results obtained from lesions of both facial nerves, taken together with the results reported in the literature, led to the conclusion that the postganglionic cholinergic nerve fibers in the pineal are of parasympathetic origin. A model for the sympathetic and parasympathetic pineal innervation is proposed.     

Aminergic innervation pattern of the rodent pineal gland: no apparent influence of time of day

Pineal melatonin synthetic activity shows distinct diurnal characteristics. The circadian regulation of melatonin synthesis is provided by noradrenaline-releasing sympathetic nerves. The pineal noradrenaline content shows a circadian rhythmicity tidally related to the changes in melatonin synthesis rate. To evaluate possible circadian changes of pineal noradrenergic fibre arrangement, the nerve distribution in rat and guinea pig pineal glands was visualized by means of glyoxylic acid-induced histofluorescence. Histochemical findings at 08.00 h and 24.00 h did not exhibit any differences: in both species a dense, mainly perivascularly located network of fluorescent fibres was encountered. As indicated by the simultaneous intraneural presence of green-bluish and yellow fluorophores these fibres most likely contain noradrenaline and serotonin. Obviously circadian melatonin synthesis changes are not paralleled by changes in the distribution pattern of pineal sympathetic nerve fibers. Like other sympathetic innervation-related morphological parameters, histofluorescence does not accurately reflect circadian biochemical changes in the pineal gland.     

An immuno-electron-microscopic study of the localization of VIP-like immunoreactivity in the adrenal gland of the rat

Summary VIP-like immunoreactivity was revealed in a few chromaffin cells, medullary ganglion cells and a plexus of varicose nerve fibers in the superficial cortex and single varicose fibers in the juxtamedullary cortex and the medulla of the rat adrenal gland. VIP-like immunoreactive chromaffin cells were polygonal in shape without any distinct cytoplasmic processes and they appeared solitarily. Their cytoplasm contained abundant granular vesicles having a round core and the immunoreactive material was localized to the granular core. VIP-immunoreactive ganglion cells were multipolar and had large intracytoplasmic vacuoles. The immunoreactive material was localized not only in a few granular vesicles but also diffusely throughout the axoplasm. VIP-immunoreactive varicose nerve fibers in the superficial cortex were characterized by abundant small clear vesicles and some large granular vesicles, while those in the juxtamedullary cortex and medulla and the ganglionic processes were characterized by abundant large clear vesicles, as well as the same vesicular elements as contained in the nerves in the superficial cortex. The immunoreactive material was localized on the granular cores and diffusely in the axoplasm in both nerves. Based on the similarity and difference in the composition of the vesicles contained in individual nerves, it is likely that the VIP-immunoreactive nerve fibers in the medulla and the juxtamedullary cortex are derived from the medullary VIP-ganglion cells, while those in the superficial cortex are of extrinsic origin. The immunoreactive nerve fibers in both the cortex and the medulla were often in direct contact with cortical cells and chromaffin cells, where no membrane specializations were formed. The immunoreactive nerve fibers were sometimes associated with the smooth muscle cells and pericytes of small blood vessels in the superficial cortex. In addition they were often seen in close apposition to the fenestrated endothelial cells in the cortex and the medulla, only a common basal lamina intervening. Several possible mechanisms by which VIP may exert its effect in the adrenal gland are discussed.     

Ultracytochemical identification of catecholamine-containing vesicles in the ligated sciatic nerve of the rat. Comparison with sympathetic nerve terminals

Summary Using the fixation procedure of Tranzer, three kinds of granular vesicles were identified in certain unmyelinated fibres of rat sciatic nerves proximal to a ligature: (1) small vesicles (SGV: 30–60 nm in diameter), (2) large vesicles (LGV: 60–100nm in diameter), and (3) large elongated vesicles (LEV: 60–100nm in diameter). A comparative study concerning the distribution of these granular vesicles was carried out using a cytopharmacological method (reserpine) and employing different fixatives (aldehydes + OsO₄, or OsO₄ alone) in periarterial nerve plexus of the femoral artery, vas deferens and the pineal organ.Use of Tranzer's method allows preservation in almost all granular vesicles of a strongly electron-dense core, while with the other fixatives mainly small, eccentric dense cores occur in the vesicles. Two main features were observed in ligated sciatic nerves: (i) a clear increase in the number of LGV, and (ii) the presence of LEV, considered as a variety of LGV rather than a new population of granular vesicles. Reserpine caused the cores of SGV to disappear almost completely, while LGV and LEV remained only partly depleted. The original method combining Tranzer's fixation procedure with radioautography revealed radioautographic labelling only in the unmyelinated fibres of ligated sciatic nerves and mainly superimposed over SGV, LGV and LEV. It is suggested that (i) SGV, LGV and also LEV represent possible storage sites of catecholamines, and (ii) a local morphogenesis of SGV from the large vesicles occurs in ligated sympathetic nerve fibres.     

Calcitonin gene-related peptide (CGRP)-like immunoreactivity in scattered chromaffin cells and nerve fibers in the adrenal gland of rats

Summary The present immunohistochemical study reveals that a small number of chromaffin cells in the rat adrenal medulla exhibit CGRP-like immunoreactivity. All CGRP-immunoreactive cells were found to be chromaffin cells without noradrenaline fluorescence; from combined immunohistochemistry and fluorescence histochemistry we suggest that these are adrenaline cells. In addition, all CGRP-immunoreactive cells simultaneously exhibited NPY-like immunoreactivity. CGRP-chromaffin cells were characterized by abundant chromaffin granules with round cores in which the immunoreactive material was densely localized. These findings suggest the co-existence of CGRP, NPY and adrenaline within the chromaffin granules in a substantial number of chromaffin cells.Thicker and thinner nerve bundles, which included CGRP-immunoreactive nerve fibers, with or without varicosities, penetrated the adrenal capsule. Most of them passed through the cortex and entered the medulla directly, whereas others were distributed in subcapsular regions and among the cortical cells of the zona glomerulosa. Here the CGRP-fibers were in close contact with cortical cells. A few of the fibers supplying the cortex extended further into the medulla. The CGRP-immunoreactive fibers in the medulla were traced among and within small clusters of chromaffin cells and around ganglion cells. The CGRP-fibers were directly apposed to both CGRP-positive and negative chromaffin cells, as well as to ganglion cells. Immunoreactive fibers, which could not be found close to blood vessels, were characterized by the presence of numerous small clear vesicles mixed with a few large granular vesicles. The immunoreactive material was localized in the large granular vesicles and also in the axoplasm. Since no ganglion cells with CGRP-like immunoreactivity were found in the adrenal gland, the CGRP-fibers are regarded as extrinsic in origin. In double-immunofluorescence staining for CGRP and SP, all the SP-immunoreactive fibers corresponded to CGRP-immunoreactive ones in the adrenal gland. This suggests that CGRP-positive fibers in the adrenal gland may be derived from the spinal ganglia, as has been demonstrated with regard to the SP-nerve fibers.     

Autonomic nerves terminating on smooth muscle cells of vessels in the pineal organ of various mammals

The significance of autonomic nerves reaching the pincal organ was already investigated in connection to the innervation of pinealocytes and mediating light information from the retina for periodic melatonin secretion. In earlier works we found that some autonomic nerve fibers are not secretomotor but terminate on arteriolar smooth muscle cells in the pineal organ of the mink (Mustela vison). Studying in serial sections the pineal organ of the mink and 15 other mammalian species in the present work, we investigated whether similar axons of vasomotor-type are generally present in the wall of pineal vessels, further, whether they reach the organ via the conarian nerves or via periarterial plexuses. In all species investigated, axons of perivasal nerve bundles were found to form terminal enlargements on the smooth muscle layer of pineal arterioles. The neuromuscular endings contain several synaptic and some granular vesicles. Axon terminals are also present around pineal veins. In serial sections, we found that the so-called conarian autonomic nerves reach the pineal organ alongside pineal veins draining into the great internal cerebral vein. Similar nerves present near arteries of the arachnoid enter the pineal meningeal capsule and septa by arterioles, both perivenous and periarterial nerves form terminals of vasomotor-type. The arteriomotor and venomotor regulation of the tone of the vessels of the pineal organ may serve the vascular support for circadian and circannual periodic changes in metabolic activity of the pineal tissue.     

Occurrence of uranaffin-positive synaptic vesicles in both adrenergic and non-adrenergic nerves of the rat anococcygeus muscle

Summary The uranaffin reaction in rat anococcygeus muscle, which receives a dual innervation of both adrenergic and non-cholinergic, non-adrenergic nerves was examined. Dense reaction product was observed in the vesicular membranes and/or the cores of some synaptic vesicles in the adrenergic nerve terminals. Occasional vesicles were filled up with dense reaction product. In the prominent population of small clear vesicles, however, no dense reaction product was observed. The number of small granular vesicles in the adrenergic nerve terminals was markedly increased after the administration of 5-hydroxydopamine (5-OHDA). These granular vesicles were moderately stained with uranaffin deposit on the cores but their limiting membranes possessed no uranaffin deposit at all.In the non-adrenergic nerve terminals, on the other hand, uranaffin deposit of variable density was observed on the cores of large granular vesicles but never on their limiting membranes or on the small clear vesicles. There was no change in the axon profiles after the administration of 5-OHDA.The possible occurrence of purines in the cores of large granular vesicles in the non-adrenergic nerves is discussed.     

PROXIMO-DISTAL TRANSPORT OF [14C]NOR-ADRENALINE AND PROTEIN IN SYMPATHETIC NERVES

Abstract— —Both [¹⁴C]noradrenaline and [¹⁴C]leucine were injected into the coeliac ganglia of cats in an attempt to label the noradrenaline and protein of the granular vesicles, so that their movement in the splenic nerves could be followed.
When a constriction was placed on the nerves, labelled noradrenaline and protein accumulated just proximal to it, but there was no such accumulation below it, nor above a second, more distal constriction placed on the same nerve. This indicated that a neural transport mechanism, rather than uptake from the circulation, was responsible for the accumulation.
Peaks of labelled noradrenaline and protein were observed to move down the axon at about 5 mm/hr. In addition a slow moving component of axonal protein, advancing at about 1 mm/day, was detected.
The results demonstrate a rapid proximo-distal movement of noradrenaline and protein which could represent the transport of granular synaptic vesicles from their site of manufacture in the cell body to their site of storage in the nerve terminals within the spleen.     

Gamma-aminobutyric acid (GABA) immunoreactivity in the mouse adrenal gland

Gamma-aminobutyric acid (GABA) immunoreactivity was revealed by immunocytochemistry in the mouse adrenal gland at the light and electron microscopic levels. Groups of weakly or faintly GABA immunoreactive chromaffin cells were often seen in the adrenal medulla. By means of immunohistochemistry combined with fluorescent microscopy, these GABA immunoreactive chromaffin cells showed noradrenaline fluorescence. The immunoreaction product was seen mainly in the granular cores of these noradrenaline cells. These results suggest the co-existence of GABA and noradrenaline within the chromaffin granules. Sometimes thick or thin bundles of GABA immunoreactive nerve fibers with or without varicosities were found running through the cortex directly into the medulla. In the medulla, GABA immunoreactive varicose nerve fibers were numerous and were often in close contact with small adrenaline cells and large ganglion cells; a few, however, surrounded clusters of the noradrenaline cells, where membrane specializations were formed. Single GABA immunoreactive nerve fibers, and thin or thick bundles of the immunoreactive varicose nerve fibers ran along the blood vessels in the medulla. The immunoreaction deposits were observed diffusely in the axoplasm and in small agranular vesicles of the GABA immunoreactive nerve fibers. Since no ganglion cells with GABA immunoreactivity were found in the adrenal gland, the GABA immunoreactive nerve fibers are regarded as extrinsic in origin.     

Central innervation of the pineal organ of the Mongolian gerbil

Nerve fibers connecting the brain with the pineal gland of the Mongolian gerbil (central pinealopetal fibers) were investigated by means of light and electron microscopy. Several myelinated fibers penetrate from the brain into the deep pineal gland, extend further into the pineal stalk and continue to the superficial portion of the pineal gland. In the centripetal direction these fibers were traced to the stria medullaris and to the habenular nuclei, where they turned laterad and then occupied a position immediately ventral to the optic tract. As shown in electron micrographs, lesions of the habenular area led to degeneration of myelinated fibers and nerve boutons in the deep pineal gland, the pineal stalk and the superficial pineal gland. Only boutons containing clear transmitter vesicles (devoid of a dense core) were observed to degenerate after the habenular lesions. On the other hand, removal of the superior cervical ganglia resulted in degeneration of boutons containing small (40 to 60 nm in diameter) dense-core vesicles. Several of the nerve fibers that penetrate into the deep pineal directly from the brain (central fibers) exhibited a positive reaction for acetylcholinesterase (AChE). AChE-positive perikarya were located in the projections of the stria medullaris, the lateral portions of the deep pineal, the area of the posterior commissure, and the periventricular gray of the mesencephalon. Such perikarya were found neither in the pineal stalk nor in the superficial pineal gland. These results present anatomical evidence that the pineal organ of the Mongolian gerbil receives multiple nervous inputs mediated by peripheral autonomic (i.e., sympathetic) nerve fibers, on the one hand, and by central fibers, on the other.     

Indications for the presence of two populations of serotonin-containing pinealocytes in the pineal complex of the golden hamster (Mesocricetus auratus)

Summary Serotonin-like immunoreactivity was investigated in the pineal complex of the golden hamster by use of the indirect immunohistochemical technique. The superficial and deep portions of the pineal gland, and also the pineal stalk exhibited an intense cellular immunoreaction for serotonin. In addition, perivascular serotonin-immunoreactive nerve fibers were observed. Some serotonin-immunoreactive processes of the pinealocytes terminated on the surface of the ventricular lumen in the pineal and suprapineal recesses, indicating a receptive or secretory function of these cells. Several serotonin-immunoreactive processes connected the deep pineal with the habenular area. One week after bilateral removal of both superior cervical ganglia the serotonin immunoreaction of the entire pineal complex was greatly decreased. However, some cells in the pineal complex, of which several exhibited a neuron-like morphology, remained intensively stained after ganglionectomy. This indicates that the indoleamine content of some cells in the pineal complex of the golden hamster is independent of the sympathetic innervation.Supported by a Grant from the Italian Society for Veterinary Sciences     

Innervation of the mink pineal gland with neuropeptide Y (NPY)-containing nerve fibers

Summary An immunohistochemical investigation of the mink pineal gland was performed by use of antibodies raised in rabbits against neuropeptide Y (NPY) and Cys-NPY (32–36)-amide recognizing neuropeptide Y with an amidation at position 36 (NPYamide). NPY-immunoreactive nerve fibers were located predominantly in the rostral part of the pineal gland and in the pineal stalk. Immunoreactive nerve fibers were found throughout the pineal gland, but the number of fibers in the caudal part of the gland was low. The fibers were present both in the perivascular spaces and between the pinealocytes. Many NPY-immunoreactive fibers were also located in the posterior and habenular commissures; some of these fibers were connected with the fibers in the rostral part of the mink pineal gland, indicating that at least some of the NPY-immunoreactive nerve fibers are of central origin. The nerve fibers immunoreactive to amidated NPY were distributed in a similar manner. However, the number of fibers immunoreactive to NPYamide was lower than the number of fibers immunoreactive to NPY itself. After removal of the superior cervical ganglia bilaterally 22 days or 12 months before sacrifice, NPY-immunoreactive nerve fibers remained in the gland. This immunohistochemical study of the mink pineal gland therefore shows that the NPY/NPYamide-immunoreactive nerve fibers innervating the pineal gland in this spegcies are a component of the central innervation or originnate from extracerebral parasympathetic ganglia.     

Inhibitory innervation to the guinea pig trachealis muscle

The inhibitory innervation of the cervical trachea was studied in situ in anesthetized male guinea pigs. We measured effects of electrical stimulation of vagal motor and sympathetic trunk nerve fibers, during atropine, on trachealis muscle tension. Effects of direct transmural stimulation of trachealis muscle were also determined. We confirmed the dual nature of the inhibitory innervation to this muscle. Vagal motor inhibitory nerves are shown to be preganglionic. Neural transmission at the level of the ganglia is characterized by filtering of high frequency action potentials. The neurotransmitter at the myoneural junction is unidentified but is not norepinephrine. Maximal relaxation accounts for about 20-40% of maximal relaxations seen with transmural stimulation of trachealis muscle in the presence of atropine. Sympathetic trunk nerve fibers are also preganglionic. Neurotransmission at the level of the ganglia is apparently 1:1 at high-action potential frequencies. Norepinephrine released presynaptically has access to smooth muscle beta- but not alpha-receptors. Maximal adrenergic relaxations account for 60-80% of total transmural stimulation relaxations. Transmural stimulation relaxations appear to be accounted for by release of neurotransmitter from sympathetic adrenergic plus vagal nonadrenergic postganglionic nerve fibers.     

Ultrastructure of the pineal gland of the tropical bat Rousettus leschenaulti

The ultrastructure of the pineal organ was studied in the tropical megachiropteran Rousettus leschenaulti. The pineal lies deep beneath the hemispheres adjacent to the third ventricle and is traversed by the habenular commissure anteriorly. Its parenchyma consists of a uniform population of light and occasional dark pinealocytes which appear to differ only in the degree of cytoplasmic staining. Pinealocytes are characterized by well developed Golgi bodies associated with numerous small vesicles, many mitochondria and polyribosomes, and frequent subsurface cisternae. Lipid droplets and elements of smooth endoplasmic reticulum are scant. Cisternae of granular endoplasmic reticulum are occasionally dilated. A distinct feature is the abundance of clear vesicles in the pinealocyte pericapillary terminals, which also frequently contain granular vesicles and a very large vacuole. The pineal is further characterized by the presence of a small number of glial cells and myelinated nerve fibers. A broad perivascular space investing numerous capillaries contains glial-cell and pinealocyte processes, collagen fibrils and abundant unmyelinated nerve fibers. Tortuous extensions of the perivascular space enter the pineal parenchyma where they come in close proximity to branched intercellular channels or canaliculi characterized by specialized junctions and microvilli. Differences between the pineal of the non-hibernating megachiropteran Rousettus and that of the hibernating microchiropteran bats, and structural similarities to the pineal of tropical rodents are discussed.     

Effects of AF64A on cholinergic neurotransmission in the sixth abdominal ganglion of the cockroach

1. The effects of ethylcholine mustard aziridinium ion (AF64A) on the cholinergic neurotransmission in the sixth abdominal ganglion of the cockroach were studied electrophysiologically and morphologically. 2. The pre- and post-synaptic compound action potentials (CAPs) elicited via electrical stimulation of the presynaptic fibers were recorded extracellularly. 3. The amplitude of both CAPs was depressed by AF64A (50-400 microM) in a concentration- and time-dependent manner. 4. At a high concentration, they were abolished but 100 microM of carbachol still evoked the postsynaptic event. 5. Electron microscopic observation of AF64A-treated ganglia showed that nerve terminals containing small lucent vesicles could not be observed but those containing dense core or large granular vesicles changed only slightly in shape. 6. These results suggest that AF64A is selectively neurotoxic for the presynaptic cholinergic neurons in the sixth abdominal ganglion of the cockroach.     

Innervation of the guinea pig spleen studied by electron microscopy

The innervation of the guinea pig spleen was investigated by electron microscopy. Unmyelinated nerve fibers in the capsulotrabecular and arterial systems were found to contain large and small granular and small agranular synaptic vesicles in their terminals and are thought to be sympathetic adrenergic in nature. They influence the contraction of the smooth muscle cells by diffusion innervation in these systems. These nerve terminals were also scattered in both the red and the white pulp. Pulp nerves wrapped by Schwann cells were further enclosed by myofibroblastic reticular cells. This condition revealed that the pulp nerves pass through the connective-tissue spaces of the reticular fibers, which contain elastic fibers, collagenous fibrils, and lamina densa-like materials of the usual basement laminae. One of the target cells for the pulp nerves is considered to be the myofibroblastic reticular cell in the reticular meshwork. Neurotransmitter substances released from the naked adrenergic nerve terminals travel through the reticular fibers and may play a role, by both close association innervation and diffusion innervation, in the contraction of reticular cells to expose the reticular fibers. At the exposed sides, connective-tissue elements of the reticular fibers are bathed with blood plasma, and the included naked nerve terminals, devoid of Schwann cells but with basement laminae of these cells, face free cells at some distance or are in close association with free cells, especially lymphocytes, macrophages, and plasma cells. The close ultrastructural relationship between the naked adrenergic nerve terminals and immunocytes strongly suggests that there is an intimate relationship between the immune system and the sympathetic nervous system through both close association innervation and diffusion innervation. Thus splenic adrenergic nerves of the guinea pig may play a triple role in 1) contraction of smooth muscle cells to regulate blood flow in the organ, 2) induction of the exposure of reticular fibers by contraction of the reticular cells in order to form a close relationship of the nerve terminals with the immunocytes, and 3) subsequent neuroimmunomodulation of the immunocytes.     

Fine structure and innervation of the avian adrenal gland

Summary Apart from cholinergic nerve fibers, which make up the main part of efferent fibers to the avian adrenal gland (Unsicker, 1973b), adrenergic, purinergic and afferent nerve fibers occur. Adrenergic nerve fibers are much more rare than cholinergic fibers. With the Falck-Hillarp fluorescence method they can be demonstrated in the capsule of the gland, in the pericapsular tissue and near blood vessels. By their green fluorescent varicosities they may be distinguished characteristically from undulating yellow fluorescent ramifications of small nerve cells which are found in the ganglia of the adrenal gland and below the capsule. The varicosities of adrenergic axons exhibit small (450 to 700 Å in diameter) and large (900 to 1300 Å in diameter) granular vesicles with a dense core which is usually situated excentrically. After the application of 6-hydroxydopamine degenerative changes appear in the varicosities. Adrenergic axons are not confined to blood vessels but can be found as well in close proximity of chromaffin cells. Probably adrenergic fibers are the axons of large ganglion cells which are situated mainly within the ganglia of the adrenal gland and in the periphery of the organ and whose dendritic endings show small granular vesicles after treatment with 6-OHDA.A third type of nerve fiber is characterized by varicosities containing dense-cored vesicles with a thin light halo, the mean diameter (1250 Å) of which exceeds that of the morphologically similar granular vesicles in cholinergic synapses. Those fibers resemble neurosecretory and purinergic axons and are therefore called p-type fibers. They cannot be stained with chromalum-hematoxyline-phloxine. Axon dilations showing aggregates of mitochondria, myelin bodies and dense-cored vesicles of different shape and diameter are considered to be afferent nerve endings. Blood vessels in the capsule of the gland are innervated by both cholinergic and adrenergic fibers.Supported by a grant from the Deutsche Forschungsgemeinschaft (Un 34/1).     

Selective uptake of noradrenaline,dopa, and 5-Hydroxytryptamine by the nervous system of Phocanema decipiens (Nematoda): A light autoradiographic and ultrastructural study

As determined by light microscopic autoradiography, parts of the nervous system of Phocanema decipiens have selective and high affinity mechanisms for the uptake of tritiated noradrenaline, dihydroxyphenylalanine (dopa) and 5-hydroxytryptamine. In the nervous system, noradrenaline is accumulated only by the four papillary nerves and two fibers in the nerve ring. The precursor dopa is also taken up by these neurons and, in addition, by the lateral nerves. 5-Hydroxytryptamine is accumulated by the three pharyngeal nerves, two cells in each lateral ganglion, and two other fibers in the nerve ring. With adjacent ultrathin sections, the labelled papillary nerve and lateral ganglion were examined ultrastructurally and found to contain various dense core vesicles which are similar to those in other aminergic neurons. The adjoining unlabelled cells of the same neurons are found, on the other hand, to contain dense agranular vesicles. With these results, the noradrenaline accumulating neurons are suggested to be noradrenergic and to contain the amine synthesizing enzymes. The lateral nerves are regarded, for the present, as dopaminergic neurons. These suggestions are in agreement with the previous demonstration of catecholaminergic neurons in this nematode. The 5-hydroxytryptamine accumulating neurons are tentatively identified as tryptaminergic.     

Structure of visual pathways in the nervous system of fresh water pulmonary molluscs

The central nervous system of freshwater pulmonary molluscs Lymnaea stagnalis and Planorbarins corneus was stained by the method of neurobiotin retrograde transport along optic nerve fibers. In the animals of both species, bodies and fibers of stained neurons are found in all ganglia except for the buccal ones. Afferent fibers of the optic nerve form a dense sensor neuropil located in a small volume of cerebral ganglia. Characteristic groups of neurons sending their processes into optic nerves both of ipsi- and of contralateral half of the body are described. Revealed among them are neurons of visceral and parietal ganglia, which simultaneously innervate both eyes as well as give projections into peripheral nerves. It is suggested that these neurons can perform function of integration of sensor signals and, on its base, regulate photosensitivity of retina as well as activity of peripheral organs. There is established the presence of bilateral connections of the mollusc eye with cells of pedal ganglia and statocysts, which seems to be the structural basis of manifestation of the known behavior forms associated with stimulation of visual inputs of the studied gastropod molluscs.