Vascular and cardiac actions of N-di-alkyl dopamine analogs

The dimethyl derivative of dopamine is the most active agent for inhibiting responses induced by sympathetic nerve stimulation. The compound is also a vasopressor. The diethyl and dipropyl derivatives slowed heart rate and lowered arterial pressure. The dibutyl derivative appeared to be inactive. On intravenous infusion into dogs, the dimethyl, diethyl and dipropyl derivatives are rapid in onset for altering blood pressure and slowing heart rate. During a 25 min infusion period there was no evidence of tachyphylaxis. Following infusion of the compounds, inhibition of response to neural stimulation and hypotensive properties were terminated within minutes. The compounds are potent, short acting inhibitors of adrenergic transmission and apparently are acting through dopamine receptors located at presynaptic sites. A ganglionic inhibitory component may also contribute to diminished adrenergic activity.