Modification of sympathetic nerve stimulation frequency-response relationship in rabbit ileum by guanethidine, bretylium and tetracaine.

Effects of low concentrations of guanethidine, bretylium and tetracaine were comparatively studied with regard to inhibitory responses of rabbit ileum to periarterial nerve stimulation at 5, 10 and 20 Hz. Guanethidine 2 X 10(-7) to 10(-6) M and bretylium 3 X 10(-6) to 3 X 10(-5) M dose-dependently and preferentially reduced responses to lower frequencies, whereas tetracaine 10(-5) to 3 X 10(-5) M reduced responses, in a dose- and frequency-dependent manner. In conclusion, the mode of adrenergic neuron blocking action of guanethidine and bretylium differs from that of local anesthetics.