Neonatal 192 IgG-saporin lesions of basal forebrain cholinergic neurons selectively impair response to spatial novelty in adult rats

The role of the developing cholinergic basal forebrain system on cognitive behaviors was examined in 7 day-old rats by giving lesions with intraventri cular injections of 192 IgG-saporin or saline. Rats were subjected to passi ve avoidance on postnatal days (PND) 22-23, water maze testing on PND 50-60 , and a open-held test (in which reactions to spatial and object novelty we re measured) on PND 54. Behavioral effects of the lesions were evident only in the open-held test with 5 objects. Unlike controls, the lesioned rats d id not detect a spatial change after a displacement of 2 of the 5 objects. Control and lesioned rats, however, showed comparable novelty responses to an unfamiliar object. Lesion effectiveness was confirmed by 75% and 84% dec reases in choline acetyltransferase activity in cortex and hippocampus. The se results suggest that the developing cholinergic system may be involved i n spatial information processing or attention to spatial modifications.