Fig. 1.

Microinjections of ionotropic neurotransmitter agonists into the PB subregion produce changes in breathing rate (f_B). A: microinjection of the glutamatergic agonist AMPA caused a marked transient increase in fictive breathing rate. B: microinjection of GABA produced bradypnea and transient apnea. Recordings from 2 different dogs. PNG, phrenic neurogram; μ-inj, microinjection injection marker; f_B, cycle-to-cycle breathing rate [breaths/min (BPM)]. Note that the dominant effect is in expiratory duration, while peak PNG is essentially unaltered.