RELATIONSHIP BETWEEN FREQUENCY OF STIMULATION AND GANGLIONIC BLOCKADE BY DRUGS

Blockade by hexamethonium of transmission in cat sympathetic ganglia was greather during stimulation with 5 pulses/sec than with 0.5 pulses/sec. Moreover, stimulation with 5 pulses/sec for 3 min prior to the administration of hexamethonium resulted in greater blockade than did prior stimulation for 30 sec. Changes in ganglionic afterpotentials that occurred during stimulation with 5 pulses/sec were abolished by ouabain or by an anticholinesterase agent, but these drugs had no effect on frequency dependent response to hexamethonium. The rate of recovery from blockade by hexamethonium was the same with stimulation at either 5 or 0.5 pulse/sec. Like hexamethonium, tetramethylammonium and potassium chloride caused ganglionic blockade that was frequency dependent. However, in ganglia perfused with Locke's solution, the blockade by tetramethylammonium was unrelated to frequency. In perfused ganglia, alterations in calcium and potassium concentrations had no effect on the frequency dependence of blockade by hexamethonium. Reduction in concentration of sodium ions appeared to increase sensitivity of ganglion transmission to blockade by hexamethonium. © 1968.