Respiratory activity in scalene muscle of the rabbit. An artefact

Unlike in the human, it has been shown in the dog that inspiratory EMG activity in scalene arise from underlying muscle layers. We tested here the origin of the activity recorded from this muscle in rabbit, hypothesizing that the presence of an EMG activity could reflect a higher mechanical advantage in that species. In 6 anaesthetized NewZeeland rabbits, EMG activity was obtained from anterior (ASc) and posterior (PSc) parts of the scalene, from the sternomastoid (SM) and from the parasternal intercostal (PS). These activities were recorded during resting breathing and against increased inspiratory resistive loads: in control, after denervation of scalene and after an additional insulation from underlying layers. At rest, PS, ASc and 4 of 6 PSc showed an activity; with mechanical loads, a huge increase in EMG integrated signal was observed in every muscles except SM that remained invariably silent. After denervation, EMG activity decreased consistently in ASc (residual activity: 34 ± 9 % with the highest...