Pre- and postsynaptic actions of serotonin on rat suprachiasmatic nucleus neurons

Zhi Gen Jiang, Koji Teshima, Yu Qin Yang, Tohru Yoshioka, Charles N. Allen

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Serotoninergic transmission is implicated in the photic and non-photic regulation of circadian rhythms. 5-HT (1-100 μM), carboxamidotryptamine (5-CT 0.1-10 μM) and (+)-8-hydroxy-dipropylaminotetraline (8-OH-DPAT, 1-30 μM) dose-dependently activated an outward current (5-100 pA) in 30% of neurons voltage-clamped at -60 mV in the suprachiasmatic nucleus (SCN) in vitro slice. EC50 values were 7.0 μM for 5-HT and 0.2 μM for 5-CT. Serotonin-induced outward current was associated with an increase in input conductance, and the current was blocked by Ba2+ (1 mM). The amplitude of the current was enhanced by depolarization, reduced by hyperpolarization, and reversed its polarity during a hyperpolarization beyond the potassium equilibrium potential. Mean amplitudes of the 5-HT outward current changed with time of the subjective circadian day. The value near CT2 (23.8 pA) was about 4 times greater than that around CT14 (6.7 pA). Cells that responded with an outward current showed four types of morphology: monopolar, simple bipolar, curly bipolar and radial shaped; they were localized in all parts of the SCN. The EPSC evoked by retino-hypothalamic-tract (RHT) stimulation was inhibited 26% but the inward current induced by exogenously applied glutamate or NMDA was not affected by serotonin agonists. Focal stimulation-induced and spontaneous IPSC but not the exogenous GABA-induced outward current were inhibited by 5-HT agonists in a subpopulation of cells. In conclusion, 5-HT regulates SCN neurons by both pre- and post-synaptic inhibitory mechanisms; the latter may play a key role in modulating SCN circadian rhythm by activation of 5-HT receptors and opening of a potassium channel. Copyright (C) 2000 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)247-256
Number of pages10
JournalBrain research
Issue number1-2
StatePublished - Jun 2 2000


  • 5-HT receptor
  • Circadian rhythm
  • GABA
  • Glutamate
  • Serotonin
  • Suprachiasmatic nucleus
  • Synaptic inhibition

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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