Tetrodotoxin blocks NPY-induced but not muscimol-induced phase advances of wheel-running activity in Syrian hamsters

K. L. Huhman, Cherie Marvel, C. F. Gillespie, E. M. Mintz, H. E. Albers

Research output: Contribution to journalArticle


During the middle of the subjective day, circadian activity rhythms in Syrian hamsters can be phase advanced by a variety of stimuli including microinjection of neuropeptide Y (NPY) or muscimol into the suprachiasmatic nucleus (SCN). It is not known, however, if these treatments shift activity rhythms by acting directly on pacemaker cells within the SCN. In the present study NPY and muscimol were microinjected with either tetrodotoxin or saline in order to determine whether classical synaptic transmission within the SCN is necessary for the phase advances produced by NPY or muscimol. Blockade of sodium-dependent action potentials within the SCN prevented NPY- but not muscimol-induced phase advances. These data, along with our previous finding that bicuculline blocks NPY-induced phase advances, suggest that NPY requires sodium-dependent action potentials within GABAergic neurons in order to phase-shift the circadian pacemaker.

Original languageEnglish (US)
Pages (from-to)176-180
Number of pages5
JournalBrain Research
Issue number1-2
Publication statusPublished - Oct 24 1997
Externally publishedYes



  • γ-Aminobutyric acid
  • Circadian rhythm
  • GABA(A)
  • Neuropeptide Y
  • Suprachiasmatic nucleus
  • Tetrodotoxin

ASJC Scopus subject areas

  • Neuroscience(all)

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