Neurochemical effects following AF64A injection into the basal nuclei of rats.

AF64A, a specific cholinergic neurotoxin, was injected into the basal nuclei of rats. The injected sites were the bilateral nucleus basalis of Meynert (NBM) and the medial septal nucleus (MSN), well known to be the nuclei of origin of the two major cholinergic pathways. The remote effects of injection were estimated by the regional choline acetyltransferase (CAT) activity in the frontal cortex, striatum and hippocampus. The injection of AF64A (1 nmol in 1 microliter) produced a reduction in the CAT activity in each projected site: NBM lesions in the frontal cortex and MSN lesions in the hippocampus after one and three weeks. Twelve weeks after the injection, the reduced CAT activity had returned to normal levels. This neurochemical effect shows plasticity and recovery with time. The injections of small amounts of AF64A (0.2 and 0.1 nmol in 1 microliter) produced no chemical changes after one week.