Immunocytochemical localization of GABA in neurons projecting to the ventrolateral nucleus of the solitary tract

To determine the origin of γ-aminobutyric acidergic (GABAergic) input to the ventrolateral solitary tract nucleus (vlnTS), we used a double-labeling procedure for retrogradely transported horseradish peroxidase (HRP) and the immunocytochemical localization of GABA. Following HRP injections into the vlnTS, double-labeled neurons were found within the Bo¨tzinger Complex. We conclude that these double-labeled cells are the inhibitory Bo¨tzinger neurons and that GABA is a likely transmitter in this respiratory nucleus.