Interaction between somatic and vagal afferent inputs in control of ventilation in 2-week-old rabbits

Abstract

Effects of saphenous nerve stimulation (SNS) on the Hering–Breuer expiratory-promoting reflex evoked by a positive tracheal pressure (P tr; 5 cmH 2O) and on the diaphragmatic EMG (EMG di), inspiratory (T i) and expiratory (T e) time, were studied in 16 urethane-anesthetized (1.2–1.6 g/kg, i.p.) spontaneously breathing 2-week-old rabbits. Positive P tr applied at the end of T i increased the subsequent T e to 255±29% (±S.E.; P<0.0001) of control. SNS (1 sec train, 2 msec pulse, 6 Hz) applied at the onset of T e, shortened this T e by 42±3% ( P<0.0001). When SNS preceded positive P tr or positive P tr preceded SNS, the T e increased to 163±20 and 184±21% of control, respectively. These responses were not different, and smaller than that provoked by the P tr test alone ( P<0.003 and 0.05, respectively). The results show that in newborns somatic afferent stimulation attenuates the vagally mediated respiratory inhibition, whether immediately before or during the vagal stimulation.