CHOLINERGIC AND ADRENERGIC INTERACTIONS IN THERMOREGULATORY CENTERS OF RAT

Systemic administration of pilocarpine causes a fall in body temperature in the rat. This effect can be reproduced by direct injection of the drug into the rostral hypothalamic thermoregulatory centers. The fall in temperature following systemic administration of pilocarpine can be attenuated or blocked by prior injection of norepinephrine into the rostral hypothalamus. Injection of α-blocking agents into the thermoregulatory centers, immediately preceding injection of norepinephrine at the same site, prevents the inhibitory effect of norepinephrine on the hypothermic response to systemic pilocarpine. It appears that temperature regulation involves a cholinergic link in the rostral hypothalamus. Catecholamines may also play a role in the control of body temperature by changing the degree of polarization of these cholinergic neurons and thus adjusting the sensitivity of the thermoregulatory centers. Such an adjustment of the membrane potentials by endogenous catecholamines could be a factor in the physiological regulation of the set point of the central thermostat. © 1969.