Recent in vitro studies reported that glycinergic inhibition was not necessary for respiratory rhythm generation in neonatal rats. Due to the limitations of these preparations there are no data regarding a potential role for central glycinergic mechanisms controlling the upper airways. In the present study, we used the arterially perfused WHBP of neonatal rats (P0-P4) which allows both kineisiological and cellular studies (see: SFN abstr. Paton et al.: Respiratory activity in the neonatal rat). To determine a role for glycinergic inhibition in upper airway control we recorded recurrent laryngeal nerve activity as an index of motor output to the glottis before and after administration of strychnine (0.5-1.5µM) to the perfusate. Strychnine caused post-inspiratory activity to shift towards the inspiratory phase (n=8). Functionally, as revealed by measuring changes in laryngeal resistance (n=7), strychnine converted the normal inspiratory glottic dilatation (seen during control) to a constriction. Exposing pos...