Drug-induced contractile responses in the isolated posterior communicating cerebral artery of the cat.

The isolated posterior communicating cerebral artery of the cat has been shown to have the ability to produce a contractile response to the following drugs; norepinephrine (NE), tyramine (Ty), 5-hydroxytryptamine (5-HT), histamine (H), acetylcholine (Ach) and potassium (K+). The changes in the contractile response were dose-dependent. The order of potencies of these vasoactive agents with respect to ED50 was: 5-HT greater than NE greater than Ach = H = Ty greater than K+. With regard to their ability to induce maximal contractile responses the order was: H = Ach greater than 5-HT = Ty greater than NE = K+. These results show that cerebral arteries are more sensitive to 5-HT than to NE, as opposed to extracranial arteries in which NE is generally the most potent vasoconstrictor agent.