ENHANCEMENT BY CESIUM IONS OF GANGLIONIC HYPERPOLARIZATION INDUCED BY DIMETHYLPHENYLPIPERAZINIUM (DMPP) AND REPETITIVE PREGANGLIONIC STIMULATION

¹ Department of Pharmacology, University of Connecticut, Schools of Medicine and Dental Medicine, McCook Hospital, Hartford, Connecticut

Cesium chloride (up to 1 mg) had no effect on transmission or the demarcation potential of untreated superior cervical ganglia of rats. By contrast, a marked increase in ganglionic hyperpolarization was noted when cesium chloride (10 µg to 1 mg) was given during the hyperpolarization produced by dimethylphenylpiperazinium (DMPP) or preganglionic stimulation. Treatment of the ganglia with ouabain or lithium ions prevented both types of hyperpolarization and the actions of cesium ions. Ganglionic blockade by lobeline, hexamethonium and procaine was unaltered by cesium chloride. In ganglia perfused with cesium chloride-containing media (5.6 to 20 mM), spontaneous firing that was sensitive to blockade by hexamethonium occurred. The firing did not occur in chronically denervated ganglia. The increased hyperpolarization produced by cesium chloride is attributed to stimulation of ion exchange in the ganglion cells, and the spontaneous firing is attributed to acetylcholine released by cesium ions from the presynaptic nerve terminals.