Modulation by mu opioid antagonism of sleep and respiration in neonatal swine

The effect of antagonists selective for mu- and delta-opioid receptor subtypes on alcohol consumption in C57BL/6 mice

Several studies have demonstrated that non-selective opioid receptor antagonists effectively reduce alcohol consumption in both animal models and at the clinical level. However, research examining the contribution of specific opioid receptor subtypes to this effect has yielded conflicting results. Some of these studies have shown that the effect is contingent upon the action of mu receptors while others have suggested that delta receptors are primarily responsible. The data reported here re-examine this question using the alcohol-preferring C57BL/6 mice. The results of this experiment demonstrate that D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP), a mu-selective antagonist, and naltrindole, a delta-selective antagonist, are equally effective at reducing alcohol consumption in a limited access model compared to a saline control group. While there was no specific comparison of the effects of these drugs on alternative appetitive behavior, neither of these drugs had effects on measured off-session food or water consumption. The results of this experiment suggest that alcohol consumption is mediated by both mu- and delta-opioid receptor subtypes.

Hypoxia, sleep and respiration in relation to opioids in developing swine

To test the role of mu and delta opioid systems in neonates during hypoxia, a total of sixteen, 4-11 (n = 7) and 26-33-day-old piglets (n = 9) were instrumented aseptically for assessment of sleep/wake states (S/W), electromyographic activities of the diaphragm and posterior cricoarytenoid muscles (EMGdi, EMG-pca, respectively), heart rate, and arterial pressures, pH and gas tensions. During daily sessions for 5 consecutive days, the piglets inhaled 10% O2/90% N2 for 10 min twice per session, first before any drug, then after either naltrexone (2 mg.kg-1 i.v.), a predominantly mu opioid antagonist, or naltrindole (4 mg.kg-1 i.v.), a specific delta opioid antagonist. During hypoxia, young, in contrast to older piglets, spent more time asleep, and increased sleep during the second half of the hypoxic exposure before, but not after each antagonist. They also exhibited, overall, higher breathing frequency, and lower slope, amplitude, area and initial area of EMGdi and EMGpca activity than older piglets. Naltrindole stimulated EMGpca activity in both age groups, and naltrexone increased the breathing frequency and slope of EMGdi in the older group. We conclude that hypoxia enhances the activation of central mu and delta opioid systems which influence S/W and respiration.

Endogenous opiates: 1991

This paper is the fourteenth installment of our annual review of research concerning the opiate system. It includes papers published during 1991 involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal 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; sex, pregnancy, and development; immunological responses; and other behaviors.