Thermoregulatory responses of the rabbit to central neural injections of sulfolane.

Systemic exposure of the rabbit to sulfolane results in hypothermia; however, the mechanism of this thermoregulatory effect is unknown. This study was designed to determine the thermoregulatory effects of sulfolane on the central nervous system (CNS) of the rabbit. Male rabbits were stereotaxically implanted with an injection cannula over the preoptic/anterior hypothalamic area (POAH) or into the lateral cerebral ventricle. POAH temperature (TPOAH), ear temperature (Te), and metabolic rate (MR) were recorded at an ambient temperature (Ta) of 15 degrees C. No changes were observed in any of the thermoregulatory indices following injections of saline or sulfolane in dosages of 100, 300, and 1000 micrograms directly into the POAH. Intracere-broventricular (ICV) injection of saline also had no effect on thermoregulation. However, ICV sulfolane in dosages of 300, 1000, and 3000 micrograms caused TPOAH to rise 0.23, 0.47, and 0.56 degrees C, respectively. This hyperthermia was significant at a dosage of 3000 micrograms. There was no change in Te or MR at these three dose levels. Microinjection of 10,000 micrograms sulfolane ICV caused a slight decrease in TPOACH for 30 min which was accompanied by an increase in Te. Following the slight decrease, TPOAH increased to + 0.54 degrees C at 120 min after injection as Te returned to baseline values. The data suggest that the previously observed thermoregulatory effects of sulfolane following systemic exposure cannot be attributed to a direct action of the parent compound on the CNS.