Respiratory activity in neonatal rats

In neonatal animals in vitro preparations have been employed widely to stud y the central control of respiration. These preparations have limitations i n that reflex afferent inputs and kinesiological studies cannot be performe d. Here, we describe an alternative in situ experimental model for studying both peripheral and central control of the respiratory system in neonatal rats. Using technology based on adult mammals, we introduce an intra-arteri ally perfused working heart-brainstem preparation (WHBP) that permits studi es on eupnoeic respiration in neonatal rats from within a few hours of birt h. Using this preparation we demonstrate a three-phase respiratory rhythm a s revealed by the activity in phrenic and recurrent laryngeal motor nerves, the respiratory modulation of laryngeal resistance and the firing patterns of respiratory neurones recorded from the ventrolateral medulla. We conclu de that the neonatal rat WHBP is an in situ preparation because it produces a respiratory rhythm similar to that of adult in vivo mammal preparations but distinct from in vitro preparations. (C) 2000 Elsevier Science B.V. All rights reserved.