Abstract
Recently the rat has become the most popular animal model for in vivo and in vitro studies of central ventilatory control. We examined the pattern of the abdominal expiratory activity in the adult and neonatal rat. In the anesthetized or decerebrate vagotomized paralyzed and artificially ventilated adult rats, the abdominal expiratory nerve showed two discharge patterns, low amplitude expiratory discharge that persisted throughout the expiratory phase (E-all activity) and late expiratory, high-amplitude bursts (E2 activity) superimposed on this steady activity. The E2 activity occurred only at the higher levels of respiratory drive (i.e. hypoxia or hypercapnia). In the decerebrate vagotomized paralyzed and artificially ventilated neonatal rats, the E-all activity was frequently observed in the abdominal nerve under control conditions. Noxious stimuli such as tail pinch increased the respiratory frequency, and enhance the inspiratory and expiratory motor activity. When FICO2 was increased, the abdominal expiratory activity was enhanced and showed biphasic discharge pattern that consisted from the pre- and post-inspiratory discharges. The pre-inspiratory discharge had larger amplitude and shorter duration than the post-inspiratory discharge in most of cases. Since the post-inspiratory discharge was usually small or indistinguishable in the adult rat, the present results suggest that the pattern of abdominal expiratory activity should change during the postnatal development. The importance of the change in the expiratory motor pattern will be discussed. [J Physiol Sci. 2007;57 Suppl:S23]
