Effects of neonatal hypoxia on brainstem cholinergic neurons-pedunculopontine nucleus and laterodorsal tegmental nucleus

Hypoxic changes in the cholinergic neurons of the pedunculopontine nucleus (PPN) and the laterodorsal tegmental nucleus (LDT) were studied morphologically using immunohistochemistry for choline acetyltransferase (ChAT). Fifty-three postnatal day (PND) 7 Sprague-Dawley rats were subjected to a hypoxic load of 8% oxygen for 5 h. The rats which survived were later sacrificed at PND 14 or 28 for histological analysis. The results were compared with those obtained from control rats. Three weeks after hypoxic load, a decrease in the number of ChAT immunoreactive cells, especially in the caudal PPN, was found, although no remarkable changes were detected in cell morphology. Since several studies support the possibility that the cholinergic system from PPN/LDT is responsible for both REM generation and the general motor inhibition during REM sleep, our results may account, in part, for the clinical features of hypoxic brain damage such as sleep disorders and abnormal muscle tonus.