The Actions of Polymyxin B and Histamine on Ganglionic Transmission

Abstract

The ganglionic effects of histamine and the histamine-liberating agent polymyxin B were studied in the cat. Nictitating membrane contractions and postganglionic action potentials were used to monitor the actions of these drugs on the superior cervical ganglion. Close arterial injections of low doses of histamine (1 μg) directly stimulated the ganglion while considerably higher doses (above 300 μg) caused a block of transmission. The two effects were due to separate and independent mechanisms. In contrast, administration of polymyxin B (100–500 μg) only caused ganglion block.The effects of histamine on the ganglion were prevented by chlorpheniramine while those of polymyxin B were potentiated by this antihistamine. The results of this study indicate that the ganglion blocking effects of polymyxin B are not mediated by released ganglionic histamine.