Evidence that endogenous thyrotropin-releasing hormone (TRH) may control vagal efferents to thyroid gland: neural inhibition by central administration of TRH antiserum.

The intracerebroventricular (i.c.v.) injection of rabbit antiserum to thyrotropin-releasing hormone (TRH) to the urethane anesthetized rat inhibited the spontaneous electrical discharge of the superior laryngeal nerve (n.sl). On the other hand, the i.c.v. injection of rabbit antiserum to somatostatin (SRIF) failed to influence the nerve activity whereas SRIF itself is capable of inhibiting the n.sl activity. These findings suggest that TRH in the brain takes a role continuously in regulating the neural activity while SRIF is involved in the neuronal circuits as an agent for the down regulation of the autonomic nervous system.