Interaction of bretylium and guanethidine on the relaxations of the rat isolated fundal strip preparation, evoked by indirect stimulation.

1. Isolated rat stomach fundal strip bathed in Krebs solution containing atropine (1 mug/ml), responded to indirect stimulation by a relaxation which was frequency dependent. These responses were blocked by phenoxybenzamine (6 mug/ml) or phentolamine (8 mug/ml).2. Strips obtained from rats previously treated with reserpine did not show relaxation to indirect stimulation. These responses were therefore adrenergic in nature.3. Bretylium (0.1-100 mug/ml) failed to block the relaxations produced by indirect stimulation, in fact relaxations were potentiated by the drug.4. Guanethidine (10 mug/ml) blocked the relaxations induced by indirect stimulation.5. Guanethidine may be taken up by adrenergic nerves actively since its action is not seen at 12 degrees C.6. Bretylium (10 mug/ml) prevented the actions of guanethidine at 37 degrees C.