Transmitterlike action of serotonin in phase shifting a rhythm for the Aplysia eye

G. Corrent, A. Eskin

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


The presence of serotonin (5-HT) and the characteristics of the phase-response curve for 5-HT indicate that 5-HT acts as a transmitter of circadian information in the Aplysia eye. Additional evidence for such a neurotransmitter role of 5-HT in the eye is presented. The isolated eye has the capacity to synthesize 5-HT from exogenous tryptophan. The receptors mediating the phase-shifting effect of 5-HT have a high affinity for 5-HT (threshold for phase shifting is less than or equal to 10(-7) M). Also these receptors demonstrate a high degree of structural specificity for 5-HT. Some structurally similar indoles to 5-HT do not cause phase shifts (5-hydroxytryptophan, 5-hydroxyindoleacetic acid), whereas others (bufotenine, tryptamine, LSD) do cause phase shifts but are less effective than 5-HT. Furthermore phase shifts in the rhythm are not produced by other monoamine neurotransmitters (dopamine, octopamine) or acetylcholine. Changes in membrane conductance to Na+, Cl-, or Ca2+ do not appear to be involved in phase shifting by 5-HT. Since large reductions in extracellular Ca2+ did not affect phase shifting by 5-HT, 5-HT is acting either directly on the circadian pacemaker cell(s) or on cells electronically coupled to the pacemaker cell(s).

Original languageEnglish (US)
Pages (from-to)R333-R338
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number2
StatePublished - 1982

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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