The effects of cocaine, chlorpheniramine and tripelennamine on the cardiac responses to sympathetic nerve stimulation.

The effects of cocaine (COC), chlorpheniramine (CHL), and tripelennamine (TRI) on the cardiac responses to sympathetic neural stimulation were compared in open-chest, anesthetized dogs. The amplitudes of the chronotropic responses were not significantly altered by any of these drugs. Similarly, the amplitudes of the inotropic responses were not affected significantly by either COC or TRI, but they were increased moderately by CHL. All three drugs prolonged the inotropic and especially the chronotropic responses. CHL and TRI, in addition to being antihistaminics, are inhibitors of the neuronal uptake of norepinephrine. Therefor, the similarity of the effects of CHL, TRI, and COC on the cardiac responses to sympathetic stimulation is probably ascribable to their inhibitory activities on the neuronal uptake mechanism.