Bilateral changes in neocortical [3H]pirenzepine and [3H]oxotremorine-M binding following unilateral lesions of the rat nucleus basalis magnocellularis: an autoradiographic study.

Neocortical choline acetyltransferase (ChAT) activity and muscarinic [3H]pirenzepine, [3H]oxotremorine-M, [3H]N-methylscopolamine ([3H]NMS; both high- and low-affinity agonist (carbachol) sites) and nicotinic [3H]acetylcholine binding were assessed both ipsi- and contralaterally 1 week and 13 weeks after unilateral ibotenic acid lesions of the rat nucleus basalis magnocellularis (NBM). Ipsilateral ChAT activity was reduced to 49% of control values 1 week postlesion but by 13 weeks had recovered to 80% of control values. Contralateral ChAT activity did not change significantly at either 1 week or 13 weeks postlesion. At 1 week postlesion, [3H]oxotremorine-M binding was increased by 33% and 54% in ipsilateral and contralateral neocortex, respectively. By week 13, both ipsi- and contralateral [3H]oxotremorine-M binding had returned to normal but [3H]pirenzepine binding was significantly decreased by 31% and 39% in the ipsilateral and contralateral hemispheres, respectively. The binding of [3H]NMS and [3H]acetylcholine did not differ significantly from control values at either 1 week or 13 weeks postlesion. These data suggest that none of the cholinergic binding sites studied is preferentially localized presynaptically and that there may be interhemispheric regulation of neocortical cholinergic binding sites.