title: Daily torpor in the absence of the suprachiasmatic nucleus in Siberian hamsters.
abstract: Siberian hamsters express torpor spontaneously after several weeks of exposure to short days. In long days, torpor is expressed only when food intake is restricted. Hamsters maintained in a long photoperiod (16 h light/day) at 15 degrees C expressed daily torpor during food restriction both before and after bilateral ablation of the suprachiasmatic nucleus (SCN). Hamsters housed in short days (8 h light/day, ambient temperature 15 degrees C) and fed ad libitum displayed torpor before, but not after, ablation of the SCN (SCNX). Torpor was reinstated in all short-day SCNX hamsters during postoperative food restriction and persisted in several animals even after ad libitum feeding was reinstated. Torpor was entrained to the light-dark cycle in both long- and short-day hamsters preoperatively but appeared to occur in a temporally random fashion in SCNX animals. SCNX hamsters, unlike control animals, displayed multiple torpor bouts per 24 h. The SCN is not essential for the expression of torpor but plays a crucial role in its temporal organization.
authors.affiliation: Department of Psychology, University of California, Berkeley 94720.
authors.forename: N F
authors.initials: NF
authors.lastname: Ruby
authors.forename: I
authors.initials: I
authors.lastname: Zucker
mesh_terms: D000818:Animals; D001831:Body Temperature; D001835:Body Weight; D002940:Circadian Rhythm; D006224:Cricetinae; D004734:Energy Metabolism; D005508:Food Deprivation; D009043:Motor Activity; D010507:Periodicity; D013493:Suprachiasmatic Nucleus / Q000502:physiology*