Ontogeny of sleep/wake and cardiorespiratory behavior in unanesthetized piglets

Abstract

Young and older piglets (2–15, 25–35 days old) underwent chronic recording of electrocorticogram, vertical and horizontal electrooculograms, electromyograms of submental muscles, diaphragm (EMG di) and posterior cricoarytenoid (EMG pca), 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, EMG di and EMG pca duration and EMG pca amplitude increased in all S/W, EMG di amplitude decreased in TS and QS and rate of rise of EMG di and EMG pca decreased in W, TS and QS. Active sleep was characterized by smaller normalized EMG pca amplitudes in the young, short EMG pca to EMG di intervals in both ages and predominance of prolonged diminished muscle activity (DMA) of either muscle. Discoordination between EMG pca and EMG di 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.