Chronic immunization of endogenous thyrotrophin-releasing hormone (TRH) in brain alters the behavioural response to pentobarbital and a TRH analogue.

Rats were infused with purified thyrotrophin-releasing hormone (TRH) anti-serum i.c.v. for two weeks and the reversal of pentobarbital-induced anaesthesia, hypothermia and respiratory depression by central administration of a TRH analogue (CG 3509) was measured. After antibody infusion the anaesthesia time was more than doubled but the responses to CG 3509 were increased, suggesting a role for endogenous TRH in arousal mechanisms which is sensitized following chronic immunological blockade.