Morphologic characteristics and responses of the neurons of the right parietal ganglion in Lymnaea stagnalis to stimulation of the sensory structures

Intracellular recordings have been made of the responses of 22 neurons of the central part of the dorsal surface of the right parietal ganglion of the snail Lymnaea stagnalis to adequate stimulation of chemo-, photo- and mechanoreceptor cells of the mantle and head skin including tentacles and lips. It was shown that the main bulk of the neurons investigated has broad receptive fields in the body wall and mantle, being able to respond to all types of the applied stimuli. Alongside, single neurons were revealed which receive single-mode input, either a mechanosensory or chemosensory one. Morphological studies indicate that the neurons are unipolar and have usually one, sometimes several projections. They differ in the pattern of branching as well as in the projections to peripheral nerves. However, almost all of them have vast dendritic regions in the central nervous system including central sensory nucleus of the right parietal ganglion.     

Electron-microscopic analysis of synapses of the inferior mesenteric sympathetic ganglion in the afferent chain of sympathetic reflexes

There are axodendritic, axosomatic, dendrodendritic, and axoaxonic synapses in the inferior sympathetic ganglia. Preliminary transectioning of the preganglionic fibers, degeneration of these fibers, and circumferential preliminary cutting of all connections of the ganglion do not give rise to structural disturbances in all of the synapses: some of them remain intact. Preliminary cutting of the hypogastric nerves — which leads to degeneration of the central ends of peripheral afferent neuron axons, above all those of Dogel' type II cells — causes structural changes of a degenerative nature in a number of ganglionic synapses, although no changes are observed in most of them. Intact and structurally changed synapses are analyzed as synapses between afferent and efferent sympathetic neurons on the one hand, and between afferent neurons of different levels of the vegetative nervous system forming visceral afferent pathways that are interrupted in the ganglion on the other.Preliminary results were published in Dokl. Akad. Nauk BSSR,2, 934–937 (1967), and presented at the First All-Union Conference on Electron Microscopy, Leningrad, 1968.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol.3, No. 1, pp. 84–88, January–February, 1971.     

Crossed and uncrossed afferent inputs of mesocerebral neurons of the mollusk Planorbis corneus

Experiments on the isolated ganglionic ring of the freshwater molluskPlanorbis corneus showed that more neurons (30%) in the ipsilateral mesocerebrum respond to stimulation of the left cerebral nerves than to stimulation of the opposite nerves (13%). A similar picture is observed for neurons of the right mesocerebrum, except that 11% of neurons respond to activation of the left cerebral nerves compared with 39% to stimulation of the ipsilateral right cerebral nerves. Ipsilateral connections of nerve of the visceral complex of ganglia are more clearly defined, as is exemplified by the left pallial nerve, during stimulation of which 68% of neurons in the ipsilateral mesocerebrum were activated, compared with 8% in the contralateral right mesocerebrum. Afferent fibers running in the visceral nerves cross at the level of the abdominal ganglion and not of the cerebral commissure, as might be expected from the structure of the ganglionic ring. The mesocerebral neurons themselves do not form synaptic connections between the mesocerebra, and excitation reaching one of them does not therefore induce any effects in the other.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 571–575, November–December, 1973.     

Microscopic localization of cholinesterases in the nervous systems of the lobsters, Panulirus argus and Homarus americanus

Using acetylthiocholine as substrate, microscopically localizable cholinesterase (ChE) activity is demonstrated in neural and glial elements of central and peripheral nervous systems of the lobsters, Panulirus argus and Homarus americanus. Moderate to very intense ChE activity occurs in all synaptic regions of the central ganglia and stomatogastric ganglion, in glial sheaths around neuron somata and peripheral nerve axons, and in cytoplasm of a few nerve cell bodies. Axons, identified as motor, contain extremely little ChE. The principal reaction in peripheral nerves occurs in sheath elements of sensory fibres; in most cases, much of the reaction is lost as the nerves lose the sheaths at the point of entry into brain.     

Distribution of biogenic amines in the slug,Limax maximus

Summary The distribution of monoamines inLimax maximus was studied by the histochemical fluorescent method of Falck and Hillarp. The number of 5-HT-containing and catecholamine-containing perikarya in the central nervous system is small compared with the non-fluorescent perikarya. However, all the ganglia except the proto-cerebral ganglia have some amine-containing neurons. There are relatively larger numbers of fluorescent cells in the cerebral, visceral, pedal and right parietal ganglia than in the other ganglia. A single, giant 5-HT-containing neuron was observed in each meta-cerebral ganglion.Monoamine neurons are localised in a number of peripheral tissues (heart, integument, tentacles, penis retractor muscle, sole of foot, kidney, alimentary canal, reproductive organs and tentacular, pharyngeal and cephalic retractor muscles). Neurons containing catecholamine are mostly associated with sensory structures such as the statocysts, the retina of the eye and the integument of the tentacles, whereas 5-HT-containing nerve fibres are mainly observed in muscle tissues.We wish to thank the Wellcome Trust for financial support.     

Chemical sensitivity of Limnaea stagnalis neurons and their responses to synaptic stimulation

Responses of nerve cells to puncture, to touching the surface of the mollusk leg, osmotic stimulation, and extracellular microiontophoretic injection of acetylcholine, noradrenalin, serotonin, atropine, and propranolol were recorded intracellularly in the right parietal, left pedal, and visceral ganglia of the unisolated circumpharyngeal ring ofLimnaea stagnalis. Selective sensitivity of the neurons to the biologically active substances was observed. Results indicative of the functional differences between the various ganglia and of their neurochemical organization were obtained. Selective blocking of the unit responses to puncture of the surface of the mollusk leg by atropine or propranolol suggests that different forms of excitation reaching the central neurons evoked different and specific neurochemical processes on their subsynaptic membranes which can retain the essential informativeness of the widely different afferent volleys converging on a single nerve cell.I. M. Sechenov First Moscow Medical Institute. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 510–518, September–October, 1973.     

Structure of visual pathways in the nervous system of freshwater pulmonate molluscs

Central nervous system of freshwater pulmonate molluscs Lymnaea stagnalis and Planorbarius corneus was stained using retrograde transport of neurobiotin in the optic tract fibers. In both species, perikarya and fibers of the stained neurons are found in all ganglia except the buccal ones. Afferent fibers of the optic nerve form dense sensory neuropil located in relatively small volume of cerebral ganglia. Typical neuronal groups sending their processes into the optic nerves of ipsilateral and contralateral body halves are described. Among them, neurons of visceral and parietal ganglia innervating both eyes concurrently as well as sending projections into peripheral nerves are revealed. These neurons, supposedly, have a function to integrate sensory signals, which may be a basis for regulation of light sensitivity of retina and functioning of peripheral organs. Bilateral links of the molluscan eye with the pedal ganglia cells and statocysts are found, which is, likely, a structural basis of certain known behavioral patterns related to stimulation of visual inputs in the studied gastropod molluscs.     

Single neurone responses to tactile stimulation of the heart in the snail,Helix pomatia L.

Summary The electrical activity of the heart nerve and of single neurons in the suboesophageal ganglia were recorded during tactile stimulation of the heart. 15 neurons were identified which responded to heart stimulation by inhibiting or accelerating activity. Cells influenced by heart afferents are scattered in the visceral and in the right and left parietal ganglia.In most of the cases both decrease and increase of cell activity are caused by synaptic potentials, in some cases, however, the neuron is assumed to have a sensory character.The activity of three neurons influenced by heart stimulation was conducted into the heart nerve. These cells are central neurons of a heart-CNS-heart reflex.Some of the neurons located in the right parietal and visceral ganglia have no connection with the mechanoreceptors of the heart. Since their spikes propagate into the heart nerve, they probably take part in the extracardial regulation of heart activity.One of the neurons located in the visceral ganglion (cell V12) sends its axon into the heart nerve. The response of this neuron to heart stimulation was an increase in activity and an inhibition of the heart rate. This is an inhibitory neuron of the extracardial heart regulatory system.     

Distribution of serotonin-containing neurons in the central nervous system of the snail Helix pomatia

Summary The distribution of serotonin (5HT)-containing neurons in the central nervous system of the snail Helix pomatia has been determined in whole-mount preparations by use of immunocytochemical and in vivo 5,6-dihydroxy-tryptamine labelling. 5HT-immunoreactive neuronal somata occur in all but the buccal and pleural ganglia. Immunoreactive fibres are present throughout the central nervous system. The 5HT-immunoreactive neuronal somata characteristically appear in groups, located mainly in the cerebral, pedal, visceral and right parietal ganglia. The majority of 5HT-immunoreactive neurons is located in the pedal ganglia. Additionally a dense network of 5HT-immunoreactive varicose fibres is found in the neural sheath of the central nervous system including all the nerves and ganglia. The number and distribution of 5HT-immunoreactive neurons correlates with that demonstrated by 5,6-dihydroxytryptamine labelling method.     

Electrophysiological study of serotoninergic neuron Cl in the pteropod mollusk Clione

Functional characteristics of cerebral serotoninergic neuron Cl, axons of which terminate at the buccal ganglia [7], were investigated in the pteropod molluskClione. Stimulating neuron Cl induced activation of the feeding rhythm generator located in the buccal ganglia — an effect arising after a long latency and persisting for some tens of seconds once stimulation had ended. Neuron Cl receives feedback from buccal ganglion cells and this brings about periodic modulation in ganglia activity during the generation of feeding rhythm. Activity of neuron Cl is correlated with operation of the locomotor rhythm generator located in the pedal ganglia. The firing rate of Cl neurons increased upon activation of the locomotor generator (whether spontaneous or induced by stimulating certain command neurons). The correlation found between workings of the locomotor generator and activity of Cl neurons is thought to be one of the manifestations of feeding synergy involving simultaneous activation of the locomotor and buccal apparatus.Institute for Research on Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 18–25, January–February, 1991.     

Conducting pathways of the dog solar plexus

Conducting pathways of the dog solar plexus were studied by recording action potentials from its nerves. The splanchnic nerves are composed of two groups of fast-conducting afferent A fibers (with conduction velocities of 12–15 and 25–56 m/sec), slowly conducting afferent C fibers (0.4–2.0 m/sec), and preganglionic B and C fibers (1.0–12.0 m/sec). Afferent A and C fibers from peripheral nerves run without interruption through the ganglia of the solar plexus, splanchnic nerves, and sympathetic chain and they enter the spinal cord in the composition of the dorsal roots. Cell bodies of A fibers are located in the spinal ganglia, those of the C fibers below the ganglia of the solar plexus, evidently in the walls of the internal organs. Peripheral nerves contain A fibers only with very low conduction velocities (13–20 m/sec) and no fast-conducting A fibers (25–56 m/sec) were found. Preganglionic fibers terminate synaptically on neurons of the ganglia of the solar plexus whose axons run in the peripheral nerves to the internal organs. Synaptic pathways run from some peripheral nerves of the solar plexus into others through its ganglia; in all probability these pathways participate in peripheral reflex arcs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 76–83, January–February, 1976.     

Subsynaptic modulation of excitatory chemical transmission produced by metacerebral neurons in the mollusk buccal ganglion

The effects of stimulating neuron LMcl (which secretes serotonin from the axonal endings) on the response of buccal cells LBc2 and LBc3 to stimulation of synaptic (predominantly cholinergic) inputs from iron peripheral neurons were investigated inHelix pomatia. Stimulation of neuron LMc1 was found to modulate such response LBc2 and LBc3 producing an increase in the former and decrease in the latter. Results of pharmacological action show the modulation of excitatory chemical transmission produced by LMc1 in the buccal ganglion to be subsynaptic.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 539–546, July–August, 1989.     

Axonal pathways of giant neurons identified in the right parietal and visceral ganglia in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac)

• 1.1. The axonal pathways of thirteen giant neurons identified in the right parietal and the visceral ganglia, found in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac), were investigated by intracellular injections of Lucifer Yellow, with regard to their axonal projections into the following six peripheral nerves: lap n (left anterior palliai nerve), lpp n (left posterior palliai nerve), int n (intestinal nerve), anal n (anal nerve), rpp n (right posterior palliai nerve) and rap n (right anterior palliai nerve).
• 2.2. These projections were confirmed by the recording of the axonal responses from the nerves.
• 3.3. On the dorsal surface of the right parietal ganglion, the following four giant neurons were identified: PON (periodically oscillating neuron), TAN (tonically autoactive neuron), RAPN (right anterior palliai neuron), and d-RPLN (dorsal-right parietal large neuron).
• 4.4. The PON axonal pathways projected into int n; those of TAN into all of the nerves examined; those of RAPN into lap n, lpp n, int n, anal n and rap n.; and those of d-RPLN into pd nn (pedal nerves) through the pedal ganglia, lpp n, anal n, rap n and sometimes lap n.
• 5.5. On the dorsal surface of the visceral ganglion, the following four giant neurons were also identified: VIN (visceral intermittently firing neuron), FAN (frequently autoactive neuron), INN (intestinal nerve neuron) and d-VLN (dorsal-visceral large neuron).
• 6.6. The VIN axonal pathways, which had no branch into the six nerves examined, went to both the right and the left pedal ganglia, sending a branch into the cerebro-pleural connective; those of FAN projected into lap n, anal n and rap n, and sometimes into lpp n and rpp n; those of INN into int n; and those of d-VLN into pd nn, lap n, lpp n, anal n and rap n.
• 7.7. On the ventral surface of the right parietal ganglion, v-RPLN (ventral-right parietal large neuron) was identified. The axonal pathways went to pd nn, lap n, lpp n, anal n and rap n.
• 8.8. On the ventral surface of the visceral ganglion, the four giant neurons, v-VNAN (ventral-visceral noisy autoactive neuron), v-VLN (ventral-visceral large neuron), r-VMN (right-visceral multiple spike neuron) and 1-VMN (left-visceral multiple spike neuron) were identified.
• 9.9. The axonal pathway of v-VNAN projected into rpp n and rap n; those of v-VLN into pd nn, lap n, anal n, rap n and sometimes to lpp n; those of r-VMN into int n and rpp n; and those of 1-VMN also into int n and rpp n.
• 10.10. The present morphologial investigations of the giant neurons confirmed well the identifications of the neurons previously studied. The axon of the neurons examined here, except for VIN, projected into some of the peripheral nerves, while the VIN axon extended into the cerebro-pleural connective.
• 11.11. The five neurons, PON, TAN, v-VNAN, r-VMN and 1-VMN, formed fine axonal arborizations terminating at the neuropile, while the arborizations of the other neurons were not clearly observed.
• 12.12. Although the anatomical structures of the portion examined of the suboesophageal ganglia are asymmetrical, three pairs of symmetrically-situated neurons, d-RPLN and d-VLN, v-RPLN and v-VLN, and r-VMN and 1-VMN, were found, indicating the existence of symmetrical components in the ganglia.

     

The morphology of the central nervous system of the barnacle,Semibalanus cariosus (Pallas)

The central nervous system of the sessile barnacle, Semibalanus cariosus (Pallas), has been studied with the particular aim of determining the locations of neuron somata in relation to peripheral nerves. This was accomplished by tracing peripheral nerves using dissection and methylene blue staining techniques, histological methods, and by permitting cobaltous chloride to diffuse via axons into ganglia (“backfilling”). The neuron maps resulting from the study reveal some well-defined sub-systems, a considerable degree of functional clumping of neuron somata, and some unexpected projections of neurons in the CNS. Neurophysiological studies based on these findings are in progress.     

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.     

Neuronal mechanisms of defense reaction to cutaneous nerve stimulation

A two-stage defense response was induced in the freshwater snailPlanorbarius corneus by stimulating the head. It consisted of the shell being rapidly lowered over the head and foot followed by the snail gradually withdrawing into its shell. These movements are performed by contracting the columellar muscle. Motoneurons of the columellar muscle were identified in the cerebral, parietal, and pedal ganglia. Stimulating the lip nerve was found to induce 2-stage excitation in motoneurons (responsible for the 2-stage muscular contraction) in preparations of central nervous system with the columellar muscle attached. The same 2-stage motoneuronal excitation can also occur spontaneously. This implies that defense reaction in the cell is at least partially a "fixed action" underlying a central mechanism or program and triggered by afferent stimuli. Activation of the central mechanism of defense response can also induce depolarization in certain columellar muscle motoneurons. This points to the existence of a feedback between neurons of the central mechanism and motoneurons.Institute of Research on Transmission of Information, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 786–795, November–December, 1990.     

Fucosyl-GM1 in Human Sensory Nervous Tissue Is a Target Antigen in Patients with Autoimmune Neuropathies

Abstract: Several gangliosides of human nervous tissues have been reported to be potential target antigens in autoimmune neuropathies. To explain the diversity of clinical symptoms in patients with antiganglioside antibodies, we have searched for ganglioside antigens that are specific to individual nervous tissues such as motoneurons, peripheral motor nerves, and sensory nerves. Although the major ganglioside compositions were not different among human peripheral motor and sensory nerves, fucosyl-GM1 was found to be expressed in sensory nervous tissue but not in spinal cord, motor nerve, and sympathetic ganglia. Sera from several patients with sensory nerve involvement also reacted with fucosyl-GM1 as well as GM1. Thus, fucosyl-GM1 may be a responsible target antigen for developing sensory symptoms in some patients with autoimmune neuropathies.     

Location of bodies of peripheral (sympathetic) afferent neurons participating in peripheral reflexes of the small intestine

Acute electrophysiological experiments on cats have shown that after preliminary decentralization of the solar plexus, accompanied by degeneration of spinal and vagal afferent and preganglionic efferent fibers in its postganglionic (mesenteric) nerves, only slow activity of the C-afferents is recorded in the peripheral segments of the mesenteric nerves instead of activity of the A-, B-, and C-fibers in the control (before degeneration). Activity of the C-afferents is intensified with the appearance of spontaneous contractions of the small intestine and also after gentle stretching of the corresponding segment of the intestine by inflation of a rubber balloon. After preliminary division of the mesenteric nerves, accompanied by degeneration of the postganglionic fibers in their peripheral segments, activity of C-afferents only also was observed, but it was much weaker than in the first series of experiments. After preliminary decentralization of the solar plexus and division of the mesenteric nerves application of a single electrical stimulus to the central part of one of the divided mesenteric nerves evokes a reflex electrical response in the other mesenteric nerves which disappears after treatment of the ganglia of the solar plexus with azamethonium bromide and also after electrical stimulation of the mesenteric nerves at 10–20 Hz. However, after decentralization only, this response was much weaker than after division of the mesenteric nerves. It is concluded that these peripheral responses of the intestinal nerves are due to excitation of two types of peripheral afferent neurons: the bodies of some lie in the small intestine and their long axons (C-afferents) run to the ganglia of the solar plexus; the bodies of the others lie in the ganglia of the solar plexus and their long axons (also C-afferents) run to the intestine, where they terminate in its receptors.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol. 6, No. 2, pp. 175–185, March–April, 1974.     

Characteristics of heterosynaptic facilitation in giant neurons of the cerebral ganglion of Planorbis corneus

Experiments on giant neurons of the cerebral ganglion of the molluskPlanorbis corneus showed that heterosynaptic facilitation even if evoked by a single uncombined stimulation of the pallial nerve, is more effective than facilitation achieved by a combination of stimulations of nerves directly entering the cerebral ganglion. The intensity of facilitation does not depend on the synaptic efficiency of the heterosynaptic input for the test neuron, but on the intensity of its connection with the other neurons surrounding the giant cell (conjecturally of neurosecretory type). This fact, and also the long latent period of manifestation and achievement of the maximum of facilitation, and its nonspecificity relative to several inputs all suggest that heterosynaptic facilitation is neurosecretory in its origin. Such a mechanism of a sharp increase in the efficiency of synaptic connections in a nerve center may play an important role in the animal's nervous activity as a whole and in the formation of temporary connections in particular, although it does not reflect the specificity of the conditioned reflex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 498–507, September–October, 1980.