Trigeminal Motor Nucleus and Pontile Respiratory Regulation

Abstract

The pontile mechanisms underlying the inspiratory off-switch are not understood in full. Recently, a role in shaping the respiratory timing has been suggested for the expiratory neuronal pool of the motor nucleus of the trigeminal nerve (NVmt) in the rabbit (3). In the present study we set out to further scrutinize the apparently novel respiratory role of the NVmt in another species, the cat. We hypothesized that if the NVmt played a role in terminating the central inspiratory activity then (i) its removal ought to extend the inspiratory phase leading to an apneustic pattern of respiration and (ii) its function could be influenced by the arterial chemoreceptor input, an important regulator of the timing mechanism. We addressed these problems by comparing the effects on neural inspiration (TI) and expiration (TE) of a block of the NVmt and the nucleus parabrachialis medialis (NPBM) - hitherto the most considered locus of the off-switch and of arterial chemoreceptor excitation by cyanide before and during the block of each structure.