Abstract
It has already been established that imipramine clinically available as an antidepressant potentiates the pressor response to noradrenaline (1-4), but depresses the same responses to tyramine, amphetamine and phenetylamine (3, 5, 6). The mechanism of the potentiation or the depression has been discussed to derive from the interference with the uptake of catecholamine into the binding site as cocaine (7-10) or from the change in the sensitiveness of effector organs caused by a depletion of the endogeneous catecholamine in a similar manner to reserpine. Furthermore, there is another possibility that imipramine potentiates the pressor response due to its adrenergic β-blocking mechanism. In the present experiments the effects of imipramine, propranolol and pronethalol on the adrenergic mechanism of the isolated rabbit's atria were comparatively investigated. The parameter used was the transmembrane potentials recorded from the right atrium and the S-A node. Responses of the potentials to the test compounds as well as the effects of the test compounds on the responses of the potentials to noradrenaline, adrenaline and isopropylnoradrenaline were observed.
