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Results for “Neural Conduction”

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At least 865 records · Page 48Linked to original sources
PubMed1987

[Differences in the cytoskeleton in inhibitory and excitatory synapses].

The cytoskeleton of afferent chemical synapses, with various ultrastructure of contact zones, was examined in the Mauthner cells of the goldfish. The synapses with combined active zones and desmosome-like specialized contacts possessed a well developed cytoskeleton consisting of filaments and microtubules oriented towards the synaptic apposition. Regular arrays of synaptic vesicles oriented in the same direction were observed beyond and near the active zones. The cytoskeleton of the synapses lacking desmosome-like formations was diffusely organized throughout the boutons. The distribution of vesicles in the vicinity of active zones was also not ordered. The role of cytoskeleton in organization of the two morphologically distinct synapses is discussed. A special function of cytoskeleton as an intermediary between synaptoplasm and membrane is regarded as a necessary basis for plasticity of excitatory rather than inhibitory synapses.

Animals↗
PubMed1986

Involvement of serotonin in the excitation of phrenic motoneurons evoked by stimulation of the raphe obscurus.

Short-latency averaged responses in the C5 phrenic nerves to electrical stimulation (2.5-80 microA; 5-80 Hz; 150 microseconds pulse duration) of raphe pallidus (RP) and raphe obscurus (RO) were investigated in anesthetized, paralyzed, and artificially ventilated cats. The responses to stimulation of RO were excitatory, whereas a mixture of inhibitory and excitatory responses of lesser magnitude were observed after stimulating in RP. The maximal response was obtained from the ventral part of RO and consisted of early and delayed excitatory responses that were of equal magnitude in both left and right C5 phrenic nerve roots. The mean latency for the early response was 2.5 +/- 0.1 msec and for the delayed response was 7.0 +/- 0.2 msec. Both responses were elicited during inspiratory phase stimulation, but only the delayed response was present during expiratory phase stimulation. The stimulus threshold of the early response was 5 microA; the delayed response was elicited at currents as small as 2.5 microA. Early and delayed responses were affected in different ways by increasing stimulus current and by increasing stimulus frequency. Intravenous administration of serotonin receptor antagonists methysergide (0.1-0.7 mg/kg), metergoline (33-244 micrograms/kg), and cinanserin (1.5-9.0 micrograms/kg) caused significant dose-related reductions in the magnitude of the delayed response, but did not significantly affect the early response. These data suggest that the early and delayed excitatory responses are mediated by different neuronal pathways. The early response does not involve serotonin release, while the later response is mediated at least in part by activation of a serotonergic pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Axonal effects of capsaicin: an electrophysiological study.

The effects of axonally applied capsaicin on the discharge activity and compound action potential of the cat vagus, saphenous and phrenic nerves and the cervical sympathetic trunk were studied under in vivo and in vitro conditions. Application of capsaicin (10(-4) M) to the vagus, saphenous and phrenic nerves resulted in the appearance of intense discharge activity which reached its maximum after 3-4 min and lasted for 15-20 min. Parallel with the increase in discharge activity, elicited by orthodromic activation induced by capsaicin, the amplitudes of the A delta and C components of an antidromically evoked compound action potential were significantly reduced. After the excitatory action of capsaicin vanished, an increase in the latency and duration and a decrease in the amplitudes of the components of the compound action potential were observed which might have led to the development of a local block of impulse propagation. These changes proved to be reversible after the removal of capsaicin from the nerve. Compound action potentials recorded from the saphenous or vagus nerves pretreated with capsaicin 3-5 days before the experiments failed to show any significant changes. It is concluded that upon direct axonal application capsaicin results in the excitation of both A delta and C fibres which is followed by a nonspecific but reversible blockade of impulse propagation. The possible significance of these transient effects of axonally applied capsaicin in term of the development of the highly specific functional impairment occurring a few days after perineural capsaicin treatment remains to be elucidated.

Action Potentials↗
PubMed1986

[Features of the antidromal and synaptic activation of neurons of the Bekhterev nucleus reticularis tegmenti pontis induced by cortico- and cerebello-fugal spiking].

Antidromic activation on the Bechterew nucleus neurons with stimulation of brachia pontis and conjunctivum as well as cerebellar central nuclei and pyramidal tract, was studied in anesthetized cats. The Bechterew nucleus neurons were found to receive direct activating inputs from brachium conjunctivum, cerebellar central nuclei and the pyramidal tract. Convergence of the inputs in single neurons was shown to exist.

Animals↗