Differential effects of DL-propranolol on norepinephrine in cerebrospinal fluid and plasma

Acute administration of DL-propranolol (5 mg/kg, subcutaneous) to cats caused a significant increase in cerebrospinal fluid (CSF) norepinephrine and a significant decrease in plasma norepinephrine. This increase in CSF norepinephrine is probably due to a reflex increase in central noradrenergic firing after beta blockade. The decrease in plasma norepinephrine reflects decreased sympathetic outflow. These results are consistent with the centrally mediated hypotensive effects of the drug.