Effects of histamine on potassium exchange between the blood and cerebrospinal fluid

Histamine is a potent vasoactive substance which causes an increase in capillary permeability in many peripheral sites. The present experiments were performed to determine whether histamine would influence the exchange of potassium between the blood and the cerebrospinal fluid (CSF). An artificial CSF was perfused through the cerebroventricular system of cats anesthetized with pentobarbital. Radioactive potassium (K 42) was either infused intravenously or added to the artificial CSF throughout the experiment. Following three CSF collection periods, a retrograde infusion of histamine was made into the lingual artery or it was added to the CSF, and three samples of CSF were collected. With the K 42 intravenously and the histamine in the artificial CSF, the net movement of K 42 into the CSF was significantly increased. Prior intravenous diphenhydramine in increasing doses progressively blocked the histamine effect on K 42 movement. Cerebroventricular perfusion of histamine caused an increase in blood pressure and carotid blood flow. These changes were blocked by either diphenhydramine or N-methylatropine. N-methylatropine did not significantly alter the effect of histamine on K 42 movement. It was concluded that the histamine enhancement of K 42 movement into the CSF did not involve changes in cerebral blood flow, cerebral blood pressure of CSF pressure.