Fig. 1.

Muscle spindle activation or electrical stimulation of the second cervical nerve evokes tonic hypoglossal nerve discharge, reduces inspiratory drive and increases vascular resistance. a Vibration of the sternomastoid muscle (STM) at 50 Hz caused a small decrease in the duration of inspiratory bursts during the stimulus (boxed area), which returned to normal upon cessation of the vibration. b Electrical stimulation of the C2 nerve at 5 Hz evokes tonic discharges in HNA, during these bouts of tonic discharge PNA is suppressed—both traces are accompanied by rectified and integrated traces (∫HNA and ∫PNA). Over the stimulation period, perfusion pressure (PP) rises with little effect upon heart rate (HR). c The suppression of PNA through 5 Hz stimulation of the C2 nerve is markedly reduced following injection of NBQX into the InM