Opiatergic mechanisms of the cardiotropic effect of acute cooling

Changes in myocardial contractility after an acute cold exposure following intracerebroventricular administration of opiate receptor agonists were studied in rat hearts isolated after Langendorff. Cold exposures were carried out individually for each animal in chambers at -10°C for 4 h. Thirty min before being exposed to cold the animals were administered in a brain ventricle 10 μl of μ- or δ-opiate receptor agonists (DAGO or DADLE, respectively). Isolation and perfusion of the hearts were performed directly after the cold exposure was over. The mechanism of reduction of myocardial contractility and coronary flow induced by an acute cold exposure is believed to include stimulation of μ-opiate receptors as one of its main components, and the effect of intracerebral hypertension on hemodynamic parameters is partially mediated through activation of δ-opiate receptors.