We studied the effect of early postnatal
hypoxia-
ischemia on cholinergic neurons in the developing rat forebrain using immunohistochemistry for
choline acetyltransferase (ChAT). In 7-day-old rat pups,
hypoxia-
ischemia was induced in one cerebral hemisphere by combining unilateral carotid
ligation with exposure to 8%
oxygen for 2.5 h. This procedure caused
brain injury in the hemisphere ipsilateral to
ligation, most prominent in the corpus striatum, hippocampus and overlying cortex. In animals sacrificed 2-3 weeks after the insult, at approximately 3 weeks of age, the density of
cholinergic cell bodies was slightly higher in the lesioned rostral caudate-putamen than the opposite side (+12%, P less than 0.05). In the more caudal portion of caudate-putamen, this effect was greater. In contrast, the size of the
cholinergic perikarya in the injured striatum was significantly reduced. Cholinergic neurons in the septum (Ch1, Ch2), globus pallidus and nucleus basalis (Ch4) were relatively unaffected. Considered together with previously reported neurochemical data, these observations suggest that the immature cholinergic neurons are less vulnerable to death from
hypoxia-
ischemia than other components of the striatum. However, differentiation of surviving
cholinergic perikarya and possibly their axonodendritic processes may be disrupted by the early insult.