ENHANCEMENT OF POSTGANGLIONIC RESPONSES TO STIMULATING AGENTS FOLLOWING REPETITIVE PREGANGLIONIC STIMULATION

¹ Department of Pharmacoloqy, Schools of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Postganglinic responses to acetylcholine (ACh), carbachol, anti tetramethylammonium chloride (TMA) were enhanced markedly following repetitive preganglionic volleys at frequencies ranging from 5 to 100 cps for durations of 10 seconds to 5 minutes. Both the amplitudes and time-courses of the responses evoked by these drugs were increased by the conditioning procedure. Hexamethonium admninistered in amounts far in excess of that required to produce a complete blockade of ganglionic transmission had no effect on the development of the enhanced responses. The prior administration of procaine prevented the development of the enhanced responses.

The findings are discussed within the framework of the existing knowledge concerning post-tetanic potentiation and are considered compatible with the concept of a presynaptic locus of action for these ganglionic stimulating agents.

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