PRENATAL COCAINE ALTERS NORMOXIC SLEEP-WAKE AND DIAPHRAGMATIC EMG PATTERNS IN PIGLETS

This study assessed in piglets the effects of prenatal cocaine adminis tration on sleep-wake states (SWS) and respiratory parameters, utilizi ng diaphragmatic electromyogram (EMG(df)) recordings during normoxia b efore and after hypoxia (0.10 F-I,F-O2, 10 min). We asked whether the respiratory effects were linked to a specific SWS, and whether there w as a difference in respiratory measures between the two normoxic condi tions. Unsedated, chronically instrumented 3-9- or 21-31-day-old pigle ts, representing distinct stages in developmental respiratory control, were used. In pre-hypoxic normoxia, prenatal piglets, cocaine enhance d sleep at the expense of wakefulness and increased EMG(di) amplitude, slope, and area under the integrated envelope (EMG(di), area) in both age groups regardless of SWS; after hypoxic exposure, the respiratory findings persisted in the young group, but disappeared in the older g roup. In the young group and regardless of SWS, interbreath interval ( t(tot)) and expiratory duration (t(tot) - t EMG(di) [duration of EMG(d i)]) were shorter in the cocaine-exposed than in the unexposed piglets , and t(tot), t EMG(di), and (t(tot) - t EMG(di)) decreased from pre- to post-hypoxic normoxia. In the older group, t(tot) and (t(tot) - t E MG(di)) differed among SWS, but were unaffected by drug treatment; t E MG(di) was higher with cocaine exposure in pre-, but not in post-hypox ic normoxia, and two-thirds of the EMG(di) measurements during post-hy poxic normoxia exhibited a similar magnitude in the drug-treated and u ntreated groups regardless of SWS. We conclude that 1) prenatal cocain e alters both SWS and EMG(di), but the EMG(di) effects are independent of SWS; and 2) the similar EMG(di) patterns in the older group after hypoxia, regardless of drug treatment, suggest that hypoxia and chroni c prenatal cocaine might alter EMG(di) by similar mechanisms. (C) 1998 Wiley-Liss, Inc.