Projections from brainstem GABAergic neurons to the phrenic nucleus.

Abstract

The phrenic motoneurons receive descending projections from premotor neurons in the brainstem.4, 10 Projections from inspiratory neurons in the dorsal and ventral respiratory groups are excitatory and are responsible for the inspiratory activity of the diaphragm. On the other hand. projections from the nucleus raphe magnus (NRM), pontine Kölliker-Fuse nucleus (KF), and Bötzinger complex (Böt. C), are inhibitory and exert inhibitory effects on phrenic inspiratory activity.1, 2, 7, 8, 12 Electrophysiological studies have suggested that GABA is the putative transmitter mediating inspiratory inhibition.11 It has been reported by Aoki et al.1, 2 that phrenic inspiratory inhibition evoked by electrical or chemical stimulation at the NRM could be blocked by microinjection into the phrenic nucleus of bicuculline (a specific GABAA receptor antagonist). Whether the GABAergic neurons (which have been reported in the NRM and Böt. C in cats6, 9) project to the phrenic nucleus remains unclear. In the present study, a combined method of retrograde WGA-HRP labeling and anti-GABA immunostaining was used to address this problem.KeywordsVestibular NucleusAmbiguus NucleusSpinal Trigeminal NucleusLateral Reticular NucleusNucleus Raphe MagnusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.