Cerebroventricular propranolol elevates cerebrospinal fluid norepinephrine and lowers blood pressure

Ventriculocisternal administration of dl- and d-propranolol produced dose-dependent increases in cerebrospinal fluid norepinephrine and reductions in blood pressure. A highly significant correlation was found between the increase in norepinephrine and the hypotensive effect. The propranolol-induced hypotension was prevented by intracisternal phentolamine. These data indicate that the hypotensive effect of centrally administered propranolol results from a drug-induced release of norepinephrine, which stimulates central alpha receptors to lower arterial pressure.