Autonomic and Behavioral Thermoregulation in Golden Hamsters Exposed Perinatally to Dioxin

Abstract

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a permanent change in thermoregulatory control of male offspring of the rat, characterized by a reduced core temperature (Tc) over a wide range of ambient temperatures (Ta). To examine the similarities in this effect across species, the thermoregulatory effects of perinatal TCDD were evaluated in the golden hamster, a species which is very resistant to the lethal effects of TCDD. Adult male hamsters exposed on Gestational Day 11.5–11.75 to 2.0 μg TCDD/kg by gavage were subjected to a variety of behavioral and autonomic thermoregulatory measurements. NocturnalTcof TCDD-treated animals was 0.4 to 1.0°C below that of controls over aTarange of 14 to 34°C. Hypothermia persisted in spite of normal metabolic responses to cold exposure. The hypothermic effect of perinatal TCDD exposure was found to persist over a 24-hr period in unrestrained hamsters monitored by radiotelemetry. The TCDD-treated hamster offspring placed in a temperature gradient exhibited a preference for warmTa’s for 2 to 3 hr; however, when maintained over a 22-hr period in the gradient there was no effect of TCDD on behavioral thermoregulation. TCDD had no effect on motor activity measured over a 24-hr period. TCDD resulted in a ∼30% reduction in body weight compared to controls; however, this weight loss appeared to have no bearing on the thermoregulatory deficiencies of the TCDD-treated animals. TCDD-treated hamsters displayed a normal metabolic response to cold exposure; thus, it would appear that perinatal exposure to TCDD leads to a dysfunction in the central control of body temperature. The perinatal effects of TCDD on thermoregulation in the rat and hamster appear to be similar.