Intracranial injection of thyrotropin releasing hormone (TRH) suppresses starvation-induced feeding and drinking in rats.

The sites at which TRH produces suppression on feeding and drinking were examined anatomically in the rat brain. This was accomplished by microinjecting nmol concentration of TRH into 6 different brain sites. Intracerebroventricular injection of TRH (25, 50, 100 nmol/rat) suppressed starvation-induced feeding and drinking in a dose related manner. The microinjection in a small amount of TRH (8 nmol/hemisphere) into the medial and lateral hypothalamus produced relatively severe anorexia and adipsia as compared with the other areas including the nucleus accumbens, the substantia nigra, the globus pallidus and the amygdala. It was concluded that the medial hypothalamus is the most sensitive site of TRH-induced anorexia and adipsia and the action of TRH on the lateral hypothalamus is also a possible mechanism mediating the decrease in water intake.