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 temperatur e were monitored during and several weeks following pyrithiamine-induc ed 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 treatmen t. Following thiamine administration and return to thiamine-fortified chow, body temperature continued to fall and several days transpired b efore body temperature and its diurnal rhythm were returned to normal. When exposed to warm and cold environments, no significant group diff erences were observed in either the maximum temperature change or the time elapsed to reach maximal temperature change. Histological examina tion 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 circ adian rhythm. These findings suggest that hypothermia and disruption o f the diurnal rhythm of body temperature can be reversed by restoratio n of adequate thiamine levels and are related to biochemical and physi ological disturbances rather than gross structural changes.