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

Young (3-13 days) and older (26-34 days) piglets were instrumented aseptically for chronic recording of sleep/wake states (biparietal electrocorticogram, horizontal and vertical electrooculogram, submental muscle electromyogram (EMG)), heart rate, arterial pressure, pH and gas tensions, posterior cricoarytenoid and diaphragmatic EMG (EMGpca, EMGdi). After recovery from surgery, piglets underwent 1 h daily recordings for 5 consecutive days. Experimental sessions comprised control periods followed by study periods with CTOP (10-40 micrograms/kg i.v.), a somatostatin analogue with mu opioid antagonistic activity. In the young group, CTOP decreased percent time spent in active sleep (AS), increased heart rate during wakefulness, increased breathing frequency during transitional and quiet sleep (TS, QS) and decreased the duration of EMGdi activity during TS, QS and AS. In the older group, CTOP decreased the duration of EMGdi activity during QS. Changes in cardiorespiratory functions with age simulated those reported previously (Scott et al. (1990) Respir. Physiol. 80: 83-102). We conclude that, in early neonatal life, the mu opioid system influences both sleep pattern and respiratory timing, and that this influence diminishes with postnatal age.