Embryonic emergence of the respiratory rhythm generator

Breathing is vital for life ex utero and therefore requires that the respiratory rhythm generator (RRG), the central neural network generating the continuous rhythmic motor command, be functional at birth. The RRG, located in the brainstem, appears to comprise two interacting respiratory oscillators: the parafacial respiratory group (pFRG), and the preBötzinger complex (preBötC). Data on the establishment of these respiratory oscillators during embryonic and foetal periods are beginning to be produced. The present paper provides a short review of the current knowledge regarding: (i) the emergence of activity in the two respiratory oscillators and (ii) their functional coupling during prenatal development in rodents.