Possible Interaction: Cocaine and Isoproterenol

“Preincubation with cocaine , 10(-5) M, shifted the inhibitory dose-response curves of Iso and Orc to the left, 16.6- and 23.3-fold respectively.”

“In the cat spleen, cocaine causes a small but significant degree of supersensitivity to isoprenaline but not to methoxamine.”

“Some responses to isoproterenol , which is not taken up by nerve terminals, were also enhanced by cocaine.”

“With prior addition of isoproterenol (ISO, 10(-8) M) or increased Ca2+ (4.0 mM) to increase cell shortening to the same degree (approximately 60%), cocaine and carbachol decreased contractility to a significantly greater extent in ISO-stimulated myocytes.”

“The concentration-response relationships for ACh and ISO were shifted to the right by cocaine (1-3 mM) when applied serosally.”

“The maximal increase in Isc induced by ISO was inhibited by serosal cocaine , but, the maximal response to ACh was not.”

“Thus, cocaine inhibits ACh-induced increases in Isc by competitively blocking the receptor and the response to ISO by noncompetitive inhibition.”

“On the other hand, cocaine administered at 58 microM suppressed DADs and triggered activity induced by overdrive in the presence of ouabain octahydrate and isoproterenol.”

“In the presence of the beta-adrenergic agonist isoproterenol , which caused a large enhancement of peak [Ca2+]i and contraction, cocaine still inhibited both parameters.”

“However, cocaine altered the response of the tissue to ACh and ISO.”

“The rapid, shallow breathing, characteristic of the Type II response, was not reversed by isoproterenol but could be prevented by blocking the vagus nerve with cocaine.”

“ Cocaine , an uptake-1 inhibitor, potentiated the contractile effect of norepinephrine but not the relaxant effect of isoproterenol or norepinephrine.”