Practice makes perfect, even for breathing

Abstract

Breathing relies on a respiratory rhythm generator. A study characterizes an early emerging oscillatory group of Phox2b-expressing parafacial cells that entrain and couple with the preBötzinger Complex at the onset of fetal breathing.

Figure 1

Development and properties of the respiratory rhythm generator, (a) Rhythmic activity appears earliest in the e-pF at E14.5 and only inconsistently drives FBMs in nVII and the hypoglossal nerve (XIIn). At E15.5, with the appearance of the preBötC, rhythmic FBMs are reliably generated. Transections do not eliminate rhythmic activity in either the e-pF or the preBötC, but the frequency is altered. After birth, the preBötC controls inspiratory motor activity, as recorded in the phrenic nerve (C4/phr), whereas a parafacial region, the pFRG/RTN, whose precursor is likely the e-pF, generates expiratory-modulated motor activity in abdominal muscles recorded in L1 and serves as a chemosensory area. (b) Schematic of the prenatal respiratory rhythm generator circuit. Arrows are schematic and may represent mono- or polysynaptic connections through intervening areas. Rhythmic activity in the e-pF is blocked by riluzole (RIL). Rhythmic activity in the preBötC can be silenced by DAMGO or CNQX.