Effects of stretch receptors of bronchi or trachea on genioglossus muscle activity.

Abstract Activity of genioglossus muscle (GG) was recorded in anesthetized rabbits at control and under SO 2 block of slowly adapting stretch receptors in thoracic airways (T) or in bronchi alone (B). At control peak activity occurred at 10% of inspiratory time, followed by a slight and a marked decrease. T and, particularly, B delayed onset and slowed rise of GG activity; then, this increased slightly under T and more under B, becoming greater than at control. During inspiratory efforts at end-expiratory volume GG activity at control was equal to that during open inspirations up to its peak, then progressively greater; during inspiratory efforts GG activity under T and B was equally smaller than at control. These findings indicate that bronchial input facilitates GG activity at end-expiratory volume and inhibits it at larger volumes: these effects are greater than those previously detected on diaphragm. Moreover, tracheal input inhibits onset and developmenta of GG activity. Under all conditions end of inspiratory activity was simultaneous in GG and in diaphragm. Time to peak inspiratory flow correlated with time to early peak in GG activity