Tetrodotoxin resets the clock.
In mammals, circadian rhythms are driven by a pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. We measured the rhythm of arginine vasopressin release in rat organotypic SCN slices following application of tetrodotoxin (TTX) or N-methyl-D-aspartate (NMDA) at various times throughout the circadian cycle. TTX resets the clock in a manner similar to dark pulses. A 4-h application of TTX starting in mid subjective day, at around circadian time (CT) 7.0, induced phase advances, while TTX treatment started in early subjective morning, at about CT 2.0, induced phase delays. On the other hand, NMDA resets the clock in a manner similar to a light pulse; that is, NMDA treatment in the early evening induced phase delays while treatment in the late night induced phase advances. The data indicate that deprivation of neuronal firing changes the circadian rhythm.
Noguchi
Takako
T
Department of Physiology, Dokkyo University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan.
Watanabe
Kazuto
K
D000818:Animals; D000831:Animals, Newborn; D001683:Biological Clocks / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D051381:Rats; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology*; D013997:Time Factors; D014668:Vasotocin / Q000378:metabolism
D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D014668:Vasotocin