EFFECTS OF TETRAETHYLAMMONIUM ON SYNAPTIC TRANSMISSION IN THE FROG SYMPATHETIC GANGLION

¹ Department of Physiology, University of Utah College of Medicine, Salt Lake City, Utah

The effects of tetraethylammonium (TEA) on synaptic transmission in time frog sympathetic ganglion were examined by recording intracellularly, and also from the postganglionic ramus. Dose-effect characteristics of transmission block by TEA, and the relation between preganglionic stimulus frequency and degree of block, were determined. Time events in transmission block by TEA included: increased latency of onset of the orthodromic spike potential, reduction in rate of rise and amplitude of the synaptic potential, and increased latency of onset of the synaptic potential. The last effect resulted from an action of TEA on the unmyelinated terminal portions of the presynaptic nerve. Simultaneously with the preceding events, the threshold for initiation of the orthodromic spike potential was reduced. Hyperpolarization of the postsynaptic membrane did not interfere with the effectiveness of TEA in reducing synaptic transmission. The effects on synaptic transmission of orthodromic and antidromic tetanization in the absence of TEA, and during partial TEA block, are described. Transmission block by TEA was antagonized by orthodromic, but not by antidromic, tetanization. The discussion considers time results in relation to current knowledge of function and morphology in frog ganglia, and to the effects of TEA and tetanic stimulation in sympathetic ganglia of other experimental animals.