Paraventricular nucleus ablation disrupts daily torpor in Siberian hamsters.
Siberian hamsters were maintained in a short-day photoperiod (8 h light/day) at 15 degrees C; body temperature (Tb) was telemetrically monitored at 10-min intervals over the course of 4 months. Animals manifesting repeated torpor bouts (Tb < 30 degrees C) were subjected to lesions of the paraventricular nucleus (PVN) or a sham operation. In the 8 weeks after surgery, 67% of the animals with complete bilateral ablation of the PVN failed to express torpor; circadian Tb rhythms, as determined by periodogram analysis, were normal in all operated and sham-operated animals. Body mass did not change in PVN-ablated animals that continued to express torpor; in contrast, rapid and sustained increases in body mass were manifested by all hamsters that terminated expression of torpor. Expression of torpor is attenuated in the absence of the PVN; it is suggested that the PVN influences torpor indirectly by regulating body mass or the availability of metabolic fuels.
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Department of Psychology, University of California, Berkeley 94720, USA.
D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D010101:Oxygen Consumption / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D017111:Phodopus; D017440:Photoperiod