CARDIAC ACTION OF DIMORPHOLAMINE

Abstract

Since the introduction of dimorpholamine (N, N'-dibutyl-N, N'-dicarboxymorpholineethylenediamine, 1064 Th) as a potent analeptic agent, not a few papers have appeared concerning its stimulating action on respiration and blood pressure. However, to the authors' knowledge, only two works have ever been published with respect to its action on the isolated heart. Using the isolated frog's heart, Fukushima (1) observed a positive inotropic action with 0.75 mg/ml of this compound, although the action was very weak and evanescent. According to his study, an isolated preparation of the dog's heart (Starling's heart-lung preparation) responded to this compound in a similar manner, whereas only a slight negative inotropic action could be induced in the isolated perfused rabbit heart. Kanda et al. (2) studied the action of dimorpholamine on the isolated frog heart. They used a higher dosage range of 0.15 to 0.3 mg/ml and found a definite positive inotropic action ; still higher doses produced more marked positive inotropic action, followed after a lapse of time by a disturbance of heart rhythm.
As an exact knowledge of the cardiac action of an analeptic is important in evaluating usefulness of that compound in clinical medicine, the authors felt the necessity to reinvestigate the cardiac action of dimorpholamine in more detail. In the course of the study, a marked positive inotropic action was observed both in the isolated frog's heart (which was essentially the same as reported by Kanda et al.) and in the heart-lung preparation of the dog. Even in the isolated perfused rabbit heart, the authors could produce a positive inotropic action under certain conditions, which the authors at present are not able to specify (see Fig. 6). This report pertains to the detailed description of the action of this potent analeptic agent on the heart-lung preparation of the dog, with special reference to the possible role played by the adrenergic mechanism in the observed positive inotropic action.