Centrally administered thyrotropin-releasing hormone exerts a well documented 
hypertensive effect. In this study, the possible physiological role of 
thyrotropin-releasing hormone in the central cardiovascular regulation was 
evaluated in spontaneously hypertensive rats receiving long-term (8-14 days) 
intracerebroventricular infusion of a heterologous antiserum to 
thyrotropin-releasing hormone. The effect of this passive immunization on the 
blood pressure was monitored from conscious animals by the tail-cuff method. 
Thyrotropin-releasing hormone antiserum significantly decreased the systolic 
arterial pressure in adult rats with established hypertension. No alterations in 
serum thyroid hormone status were observed indicating that the antihypertensive 
effect of immunological blockade of thyrotropin-releasing hormone was not due to 
changes in the serum thyroid hormone levels. These results provide evidence for 
a role of endogenous brain thyrotropin-releasing hormone in the maintenance of 
hypertension in spontaneously hypertensive rats.