Effect of intrathecal and intracarotid administration of ketamine on blood pressure and heart rate in rats.

Intrathecal and intracarotid effects of ketamine were investigated in anaesthetized rats. Ketamine was administered in the subarachnoid space in doses ranging from 300 to 1500 micrograms X kg-1. In these doses ketamine produced a short-lasting hypotension and bradycardia which may be due to inhibition of sympathetic outflow from thoraco-lumbar region. On the other hand when ketamine (5 mg X kg-1) was injected into the cerebral circulation it produced a rise in blood pressure and heart rate, probably through a cholinergic mechanism.