Effect of hypoxia on the activity of respiratory and non-respiratory modulated retrotrapezoid neurons of the cat

The retrotrapezoid nucleus (RTN), a part of the rostral ventrolateral medul la, is involved in the control of breathing. A recent immunohistological st udy suggested a possible involvement of the RTN in hypoxic chemoreflex loop . The present electrophysiological study performed in the cat demonstrates that 23 out of 24 RTN neurons were stimulated during the biphasic respirato ry response to hypoxia, which consists of a reinforcement followed by a dep ression of respiratory activity. This confirms the previous immunohistologi cal study. While 15 RTN neurons might integrate either phase I (n=7) or pha se II (n=8) O-2-chemosensitive inputs, the remaining eight RTN neurons stim ulated by hypoxia are susceptible to integrate both phase I and phase II O- 2-chemosensitive inputs. In conclusion, our results suggest that the differ ent subsets of RTN neurons may influence respiratory output by conveying si gnals originating from peripheral and/or central chemoreceptors stimulated during hypoxia. (C) 2000 Elsevier Science B.V. All rights reserved.