Basal forebrain cholinergic neurons in aged rat brain are more susceptible to ibotenate-induced degeneration than neurons in young adult brain

Choline acetyltransferase (ChAT) activity, acetylcholinesterase (AChE) activity, and [³H]nicotine binding site density were measured in neocortex from unoperated (control) and nucleus basalis (NB)-lesioned young (2-3 months old) and aged (23-24 months old) rats. In control animals, neither enzyme activities nor the density of nicotine binding sites were altered as a function of age. However, age-related differences were apparent 2 weeks following unilateral infusions of ibotenic acid into the right NB. NB lesion-induced decreases by enzyme activities were significantly greater in ipsilateral neocortices from aged rats; ChAT and AChE activities in young animals decreased by 59 and 53%, respectively, while both enzyme activities in aged rats decreased by 72%. NB lesions decreased significantly the density of nicotine binding sites in ipsilateral neocortices from both young and aged rats; binding decreased by 23-26% in young rats and by 31-34% in aged animals. Results indicate that the basal forebrain cholinergic system in the aged rat is more susceptible to ibotenate-induced degeneration than neurons in young animals.