Ontogeny of sleep/wake and cardiorespiratory behavior in unanesthetized piglets.

Young and older piglets (2-15, 25-35 days old) underwent chronic recording of electrocorticogram, vertical and horizontal electrooculograms, electromyograms of submental muscles, diaphragm (EMGdi) and posterior cricoarytenoid (EMGpca), and heart rate, arterial pressure, pH and gas tensions. With age, (1) the distribution of percent time spent in various sleep-wake states differed; (2) heart rate decreased in all S/W, arterial pressure increased in wakefulness (W), transitional sleep (TS) and quiet sleep (QS); (3) respiratory frequency decreased, EMGdi and EMGpca duration and EMGpca amplitude increased in all S/W, EMGdi amplitude decreased in TS and QS and rate of rise of EMGdi and EMGpca decreased in W, TS and QS. Active sleep was characterized by smaller normalized EMGpca amplitudes in the young, short EMGpca to EMGdi intervals in both ages and predominance of prolonged diminished muscle activity (DMA) of either muscle. Discoordination between EMGpca and EMGdi activation and the occurrence of DMA were influenced by youth and male gender. These results provide insight into subtle expressions of gender and sleep influences on developmental respiratory control.