EFFECTS OF EXCITOTOXIC LESIONS OF THE NUCLEUS BASALIS MAGNOCELLULARISON CONDITIONED TASTE-AVERSION AND INHIBITORY AVOIDANCE IN THE RAT

The role of the nucleus basalis magnocellularis (NBM) in a variety of learning tasks is well known. Lesions of this nucleus result in a redu ction of cholinergic transmission throughout a vast portion of the cor tex. Because cholinergic transmission in the insular cortex seems to b e important for the acquisition of conditioned taste aversion, the aim of the present work was to study the effects of bilateral chemically induced lesions of the NBM on this conditioning, as correlated with so me cholinergic markers in the insular cortex. The effect on inhibitory avoidance was also studied. Lesions prevented the acquisition of the aversion and disrupted retention of the task in previously trained ani mals. Learning in the inhibitory avoidance paradigm was also notably a ffected. Postlesion reductions of choline acetyltransferase and acetyl cholinesterase activities and of K+-stimulated [H-3]acetylcholine rele ase were found in the insular cortex. Further, in intact rats labeling of NBM neurons was observed by retrograde tracing after injection of Fluoro-Gold into the insular cortex. These findings indicate that the NBM is involved in the neural integration of feeding behavior and that its cholinergic projection to the insular cortex is one of the implic ated neurotransmitter systems.