Involvement of endogenous thyrotropin-releasing hormone in central regulation of the cardiovascular system after bleeding in conscious rats.

The 4th ventricle of a conscious rat was perfused using a push-pull cannula. The concentration of thyrotropin-releasing hormone (TRH) in the perfusate was significantly increased after withdrawal of 30% of the total blood. Administration of antiserum of TRH into the ventricle potentiated and prolonged the hypotension induced by the bleeding. These results suggest that endogenous brain TRH is involved in the central regulation of the cardiovascular system after bleeding in conscious rats.