Morphine and morphiceptin increase the threshold for epinephrine-induced cardiac arrhythmias in the rat through brain mu opioid receptors

Magnesium deficiency in adult rats promotes the induction of ventricular tachycardia by the administration of epinephrine

The effects of magnesium deficiency on epinephrine-induced ventricular tachyarrhythmia were investigated in adult rats. Forty-two adult Wistar rats were fed a magnesium-deficient diet while 30 rats were fed a standard diet for 20 days. The plasma magnesium concentration was lower in the magnesium-deficient rats (0.22+/-0.01 mmol/l) than in the control rats (0.76+/-0.03 mmol/l, P < 0.001). Using a telemetry system, electrocardiograms and arterial blood pressure were recorded on a polygraph in an unrestrained condition. Epinephrine was infused intravenously starting at 5 microg/kg per minute. The QT interval was prolonged to 50+/-1 ms in the magnesium-deficient rats compared with 44+/-1 ms in the control rats (P < 0.001). Before the administration of epinephrine, no ventricular tachyarrhythmias or seizures were found in either the control or the magnesium-deficient rats. The incidence of epinephrine-induced sustained ventricular tachycardia (VT) was higher in the magnesium-deficient rats (86%) than in the control rats (43%, P < 0.01). However, this VT did not result in sudden death. Seizures always preceded death in both the magnesium-deficient and control rats while the arrhythmias observed immediately before death were mainly bradyarrhythmias. The present study in an adult rat magnesium-deficient model revealed that magnesium deficiency enhances the susceptibility to epinephrine-induced ventricular tachyarrhythmias.

Participation of central kappa-opioid receptor in arrhythmogenesis

The effect of kappa receptors agonists and antagonists was studied in the model of epinephrine induced arrhythmias. Kappa receptor agonists U-50,488 and [D-Ala2]-Dynorphin A (1-13) administered I.C.V. potentiate the arrhythmogenic effect of epinephrine. The effect of U-50,488 was completely blocked by kappa receptor antagonist, nor-binaltorphine. Administration of N-cholinergic receptor inhibitor, hexamethonium, prevented pro-arrhythmic effects of U-50,488 and [D-Ala2]-Dynorphin A (1-13). The data support the hypothesis that central kappa opioid receptors play an important role in the arrhythmogenesis.

Endogenous opiates: 1993

This paper is the sixteenth installment of our annual review of research concerning the opiate system. It is restricted to papers published during 1993 that concern the behavioral effects of the endogenous opiate peptides, and does not include papers dealing only with their analgesic properties. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; development; immunological responses; and other behaviors.