title: Effects of inorganic potassium channel blockers on calcium requirement of transmission in a sympathetic ganglion.
abstract: The effects of the alkali metal ions cesium (Cs+) and rubidium (Rb+) and alkaline earth metal ions barium (Ba2+) and strontium (Sr2+) on ganglionic transmission in various calcium (Ca2+) concentrations were investigated in rat isolated superior cervical ganglia. Cesium (1 and 2 mM) moderately supported transmission in low Ca2+ and potentiated the compound action potential (CAP) at high Ca2+ concentration. Higher concentrations of Cs+ caused depression of CAP especially at lower Ca2+ concentration. Cesium (1-4 mM) induced large spontaneous rhythmic spikes or burst of spikes. At 4 mM, Rb+ potentiated CAP at all Ca2+ concentrations. As with Cs+, higher concentrations of Rb+ inhibited CAP except at large Ca2+ concentrations. Barium (1-6 mM) effectively enhanced transmission at all Ca2+ concentrations. Strontium enhanced transmission only at very low Ca2+ concentrations. No enhancement was seen with Sr2+ in the presence of normal or higher Ca2+. The results indicate that Cs+ and Rb+ may antagonize Ca2+ effects at release sites while allowing more Ca2+ influx into the nerve terminal as a result of K+ channel blockade. Barium and to a lesser extent Sr2+ may substitute for Ca2+ in the process of transmitter release in the superior cervical ganglia of rats.
authors.affiliation: Department of Pharmacology, College of Pharmacy, University of Houston, TX 77204-5515.
authors.forename: K A
authors.initials: KA
authors.lastname: Alkadhi
authors.forename: J E
authors.initials: JE
authors.lastname: Simples
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology*; D005728:Ganglia, Sympathetic / Q000187:drug effects* / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000494:pharmacology*; D015290:Second Messenger Systems / Q000187:drug effects*; D013324:Strontium / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D015221:Potassium Channels; D002586:Cesium; D001464:Barium; D012413:Rubidium; D002118:Calcium; D013324:Strontium