Opiate agonist depression of myocardial function is dose related and independent of pentobarbital or chloral hydrate anesthesia.

Previous work has demonstrated that a common opiate agonist, morphine sulfate (MS), causes significant depression of myocardial performance when added to the perfusate of a modified Langendorff isolated rat heart preparation. The same model has been used in this study with the addition of higher concentrations of MS to demonstrate that the aforementioned effects occur in a dose-related fashion. In addition, different anesthetics, sodium pentobarbital (P) or chloral hydrate (CH), were compared and demonstrated that there was no significant difference in results. This implies that there is not an anesthetic-morphine interaction occurring. These results suggest opiate agonist depression of myocardial function acts on opiate receptors, causing primarily a chronotropic effect.