Thiamine deficiency-induced disruptions in the diurnal rhythm and regulation of body temperature in the rat.

In the present study, diurnal rhythm and regulation of body temperature were monitored during and several weeks following pyrithiamine-induced thiamine deficiency (PTD group, n=8) or pairfeeding (control group, n=9). A significant decline of core body temperature and a disruption of its diurnal rhythm were observed at varying stages of PTD treatment. Following thiamine administration and return to thiamine-fortified chow, body temperature continued to fall and several days transpired before body temperature and its diurnal rhythm were returned to normal. When exposed to warm and cold environments, no significant group differences were observed in either the maximum temperature change or the time elapsed to reach maximal temperature change. Histological examination revealed necrotic lesions in thalamus and mammillary body in the PTD group characteristic of Wernicke's encephalopathy. No significant damage was observed in the medial preoptic and suprachiasmatic nuclei, brain regions involved in the regulation of body temperature and circadian rhythm. These findings suggest that hypothermia and disruption of the diurnal rhythm of body temperature can be reversed by restoration of adequate thiamine levels and are related to biochemical and physiological disturbances rather than gross structural changes.