Combined serotonergic-cholinergic lesions do not disrupt memory in rats.

Rats were trained on a delayed nonmatching to position task, divided into four groups and given the following lesions: (a) SHAM (vehicle injection into nucleus basalis magnocellularis (NBM) and raphé nuclei (RN), (b) RN (5,7-dihydroxytryptamine lesions of raphé, vehicle into NBM), (c) NBM (quisqualic acid lesion of NBM, vehicle into RN), and (d) COMB (lesions of both RN and NBM). RN lesions had no effect on performance measures including accuracy (percent correct), errors of omission, bias, latencies, and magazine response rate. NBM lesions produced delay-independent (nonmnemonic) disruptions, but performance improved over the 20 days' test. The effects of COMB lesions were no worse than NBM lesions alone. The results suggest that (a) the serotonergic system is not essential for performance in this task, (b) NBM lesions transiently impair nonmnemonic aspects of performance, and (c) serotonergic-cholinergic interactions may not be essential for some cognitive processes.