PONTINE CHOLINERGIC RESPIRATORY DEPRESSION IN NEONATAL AND YOUNG-RATS

We postulated that activation of pontine cholinergic mechanisms would cause respiratory depression in neonatal and young rats. Phrenic activ ity was recorded in decerebrate, paralyzed, ventilated and vagotomized rats of 4 to 22 days after birth. Small volumes (10-60 nl) of carbach ol (44-88 mM) were injected into the medial portion of the rostral pen s. The injection of carbachol, but not saline, decreased phrenic peak activity (83 +/- 6% of control) and respiratory frequency (64 +/- 9.5% of control) within 2 min following the injection in neonates and the depression lasted for less than 10 min. The site of injection in the p ontine reticular formation was confirmed by histology. Results suggest that cholinergic mechanisms in the medial pens depress respiratory ac tivity in the neonate.