Abstract
The parafacial respiratory group/retrotrapezoid nucleus (pFRG/RTN) and preBotzinger complex/ventral respiratory group (preBotC/VRG) are considered to play key roles in respiratory rhythm generation. To test our hypothesis that responses of these two areas to respiratory and metabolic acidosis are different, we analyzed respiratory population activities in pFRG/RTN and preBot/VRG to respiratory and metabolic acidosis by voltage-imaging. CO2/pH changes induced respiratory phase switching in pFRG/RTN bidirectionally, i.e., from preinspiratory/inspiratory phase dominant to inspiratory/postinspiratory phase dominant pattern and vice versa in 20% of preparations. These switching patterns were unpredictable. Respiratory acidosis induced recruitment of respiratory-modulated neuronal activity, although pixels that gained and lost respiratory modulation were intermingled. Among the newly recruited pixels, the preinspiratory pattern appeared mainly in pFRG/RTN and the inspiratory pattern mainly in the caudal portion of preBotC/VRG. Metabolic acidosis changed the respiratory-modulated pattern from preinspiratory dominant to inspiratory dominant in pFRG/RTN. In pixels of pFRG/RTN and the caudal portion of preBotC/VRG, respiratory and metabolic acidosis induced deprivation of respiratory modulation. We conclude that respiratory and metabolic acidosis differently affect pFRG/RTN and preBotC/VRG, induce phase switching and phase shifts in pFRG/RTN, and even alter the mechanism of respiratory rhythm generation. [J Physiol Sci. 2007;57 Suppl:S212]
