VENTRAL MEDULLARY SURFACE RESPONSES TO HYPOXIC AND HYPEROXIC TRANSIENT VENTILATORY CHALLENGES IN THE CAT

Carotid body afferent contributions to activity of the intermediate ar ea of the ventral medullary surface (IVMS) following transient hypoxia and hyperoxia were examined in 6 spontaneously breathing, pentobarbit al-anesthetized cats. Two tidal breaths of 100% N-2, 100% O-2, or room air, were randomly administered before and after carotid sinus denerv ation (CSD). Images of scattered light from the IVMS showed that activ ity increased with hypoxia (10.1 +/- 2.4%), and decreased with hyperox ia (4.8 +/- 1.8%). CSD significantly increased the magnitude and delay ed the onset of the hypoxic response, but reversed the initial compone nt of the hyperoxic response. We conclude that carotid body afferents modulate the magnitude and timing of IVMS responses to transient respi ratory challenges.