[Pressor response to the stimulation of peripheral sympathetic nerves and the posterior hypothalamus in the presence of tricyclic antidepressive agents and nomifensine in dogs].

Acute experiments documented the peripheric action of tricyclic antidepressives (imipramine, chlorimipramine and amitriptyline). They evoked a significant hypotensive action (P less than 0.02), baroreceptor blockade and higher intensity and duration of pressor responses to exogenous noradrenaline, electric stimulation of the sympathetic nerves of the spleen, posterior hypothalamus or the central extremity of vagus nerve. These effects could be produced by the inhibition of noradrenaline reuptake and are antagonized by noradrenergic blockade with phentolamine. Nomifensine does not change arterial pressure, but its analeptic effect is able to awake anesthetized dogs. The pressor noradrenergic response is greater than that obtained with tricyclic antidepressives. The potentiation showed by the injection of dopamine was similar to that produced by imipramine. Injected into the cerebral ventricles of the dog, it did not changed arterial pressure, but crossed the blood-brain barrier. High doses of tricyclic antidepressives and nomifensine evoked inhibitory effects on adrenergic responses.