Mapping of the excitatory, inhibitory, and modulatory afferent projections to the anatomically defined active expiratory oscillator in adult male rats.

The lateral parafacial region (pF ; which encompasses the parafacial respiratory group, pFRG) is a conditional oscillator that drives active expiration during periods of high respiratory demand, and increases ventilation through the recruitment of expiratory muscles. The pF activity is highly modulated, and systematic analysis of its afferent projections is required to understand its connectivity and modulatory control. We combined a viral retrograde tracing approach to map direct brainstem projections to the putative location of pF , with RNAScope and immunofluorescence to identify the neurochemical phenotype of the projecting neurons.