Brain temperature in the rat midbrain reticular formation is regulated by bombesin and TRH

We investigated the effects of intraventricular (ivt) injection of bombesin on the TRH-induced increase in temperature in the midbrain reticular formation (mrf) of the rat brain under pentobarbital anesthesia. Ivt injection of TRH in a dose of 3 nmol significantly antagonized the decrease in brain temperature induced by pentobarbital, and this antagonistic action of TRH was dose-related. Ivt injection of 3-300 pmol bombesin produced a dose-related decrease in brain temperature in response to 3 nmol TRH injection. The present data provide evidence that bombesin and TRH produce opposite actions on thermoregulation of the mrf in the rat.