[Change in the reactions of isolated vascular segments under the action of hypotensive agents]

It was shown that reactions of isolated vascular segments to electric stimulation changed in character under the effect of reserpine, ornid, benzanidine, and aldomet. Replacement of contraction by relaxation is characteristic of all hypotensive agents. This is revealed on preparations which respond initially by equivocal reactions (relaxation and contraction) depending on the intensity of the stimulation. The replacement of the sign of the reaction is marked by certain peculiarities in the case of each agent. The possibility of contraction is maintained only in response to a high dose of stimulation on condition that benzanidine and aldomet are administered. Under the effect of reserpine and ornid, initially unequivocal reactions are replaced at first by two-phase reactions (contraction then relaxation) and then by single phase (relaxation); under the effect of benzanidine and aldomet they are sharply weakened.