RESUMEN
The effects of trichlorphon on ganglionic transmission of the isolated superior cervical, ganglia of the guinea pig were investigated by means of intracellular recording techniques. At the concentration of 0.05 ?mol/L or less, trichlorphon increased the amplitude and duration of the fast excitatory postsynaptic potential ( f-KPSP ) and the membrane apolarization induced by application of acetylcholine ( ACh), but not carbachol ( CaCh ) . At the concentration of 0.1 mmol/L or more, trichlorphon reversibly depressed the f-EPSP and depolarization evoked by superfusion of either ACh or CaCh. Furthermore, the depressant effect of trichlorphon persisted in a low Ca/ high Mg solution. The membrane potential and membrane resistance of the sympathetic neurons were not significantly altered by trichlorphon.The results indicate that the facilitatory action of trichlorphon appears to be related to its anticholinesterase activity,whereas trich-lorphon-induced blockade of transmission may be explained by a direct action of trichlorphon on the postsynaptic membrane.