Modulation of electrical activity by 5-hydroxytryptamine in crayfish neurosecretory cells.
The effect of 5-hydroxytryptamine (5-HT) was tested in a population of X organ neurosecretory cells in the eyestalk of the crayfish Procambarus clarkii. Tests were conducted both in situ and on isolated neurones kept in culture. The application of 5-HT induced action potentials in silent cells. In spontaneously active neurones, 5-HT increased the firing rate and either induced firing or enhanced bursting activity. The effect of 5-HT was dose-dependent within the range 1-100 micromol l-1 in cells of the intact organ. The effect persisted for 20-30 min after 5-HT had been removed from the bathing solution. Successive applications of 5-HT onto the same neurone reduced responsiveness, suggesting that desensitization had occurred. The effects of 5-HT were blocked by prior incubation with the 5-HT antagonist methysergide. In X organ cells whose axons and branches in the neuropile had been severed, 5-HT induced a depolarisation associated with a slow inward current. In X organ neurones isolated from the eyestalk and kept in culture, 5-HT was capable of evoking bursts of action potentials and elicited a slow inward current. This effect was also blocked by methysergide (10(-4 )mol l-1). These results suggest a direct modulatory effect of 5-HT on the pattern of electrical activity in the X organ cells.
Sáenz
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F
Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, IPN, México.
García
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U
Aréchiga
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U
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003400:Astacoidea / Q000187:drug effects* / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology* / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology
D018377:Neurotransmitter Agents; D012702:Serotonin Antagonists; D012701:Serotonin; D008784:Methysergide