Some Factors Affecting the Neuron Blocking Action of Guanethidine, Xylocholine, Bretylium and Debrisoquin

The uptake of guanethidine (3.3 × 10−5 M), debrisoquin (8.4 ×10−4 M), bretylium (5.0 × 10−4 M) and xylocholine (1.0 × 10−3 M) by adrenergic neuron was studied indirectly by testing the ability of noradrenaline (NA) regarding low temp, or sodium-deprivation to prevent or reverse adrenergic neuron blocking action in the indirectly stimulated guinea-pig hypogastric nerve vas deferens preparations. NA (3.0 × 10−3 M) completely prevented the neuron blocking action of all the four blockers but reversed only that of bretylium. Exposure of preparations to a low temp. (0°C) prevented the neuron blocking action of all the four blockers but did not reverse that of any one blocker. The adrenergic neuron blocking action of guanethidine was partially prevented but was not reversed by sodium-deprivation. Sodium-deprivation neither prevented nor reversed the neuron blocking action of the other three blockers. It is concluded that guanethidine shares the uptake mechanism of NA for transport across the neuron while debrisoquin, bretylium and xylocholine appear to be transported differently.