THE DEPLETION OF CATECHOLAMINE OF THE RABBIT’S ATRIA BY RESERPlNE IN VITRO

Abstract

The depletion of serotonin and catecholamine from the tissues by reserpine in vivo and in vitro has been confirmed by many authors. The release of catecholamine from the hearts of various mammals in vivo by reserpine was already shown by Bertler et al. (1), Paasonen and Krayer (2), Waud et al. (3). Carlsson et al. (4), reported that the intravenous administration of 5 to 10 μg/kg of reserpine in rabbit decreased the content of heart catecholamine (noradrenaline) significantly, while the same procedure did not affect the content of brain catecholamine. The .sim.ilar results were also obtained by Orlans et al. (5). Higuchi et al. (6, 7) in this laboratory showed that the depletion of catecholamine in the heart of rabbit which had been injected 0.1 to 1.0 mg/kg of reserpine 24 hours before, was about 90% of the normal content. Tachi (8) in this laboratory has found that the administration of 10-6 of reserpine to the atrial preparation of rabbit revealed negative chronotropic and inotropic actions, and that the same procedure of above 10-5 of reserpine abolished the rhythmic contraction of the preparation within 60 to 120 minutes after the administration of the drug. Toda (9) in this laboratory has studied the effects of reserpine on the transmembrane potential of the pacemaker and non-pacemaker fibers of the extirpated rabbit's atrium, and also showed that reserpine in the concentration of above 10-5 depressed the potential and at last abolished it. Further, they (Tachi, Toda) have showed that although the replacement of reserpine-Ringer solution in the organ bath with normal Ringer solution did not restart the rhythmic contraction of the auricle and the rhythmic changes of the pacemaker and non-pacemaker potentials, both rhythmic patterns of the atria recovered in response to definite doses of adrenaline or noradrenaline. From the results it is suggested that the catecholamine which is subjected to release by reserpine might have a determining role in the initiation and maintenance of rhythmic contraction of the heart. Pepeu et al. (10) studied the effect of reserpine on the catecholamine content in the extirpated guinea pig's heart, suspended in Tyrode-bicarbonate solution, and found some decrease of catecholamine at 6 hours after the administration of 10-5 of reserpine. In the present experiment the effects of reserpine, iproniazid, and SKF 385 have been studied. It has been expected that the depressive effect of reserpine on the rhythmic contraction of the preparation might have some correlation with the depletion of the catecholamine,