BEHAVIORAL AND BIOCHEMICAL CONSEQUENCES OF COMBINED LESIONS OF THE MEDIAL SEPTUM DIAGONAL BAND AND NUCLEUS BASALIS IN THE RAT WHEN IBOTENICACID, QUISQUALIC ACID, AND AMPA ARE USED

Combined lesions in the medial septum/diagonal band and nucleus basali s magnocellularis (NBM) in rats were produced using three excitotoxins , ibotenate (Ibo), quisqualate (Quis), and AMPA. Reductions in choline acetyltransferase (ChAT) activity differed in the cortical regions fo r the three toxins (AMPA > Quis > Ibo), but were fairly similar in the hippocampus. ChAT activities were not reduced in the globus pallidus, but AMPA reduced ChAT in the amygdala. Lesions with all three toxins produced similar decrements in hippocampal and posterior cortical sero tonin levels. A small reduction in posterior cortical norepinephrine w as detected for Quis and Ibo lesions, Spatial memory impairments were found for all three toxin groups compared with controls in acquisition , platform reversal, and a spatial probe in the water maze. The learni ng deficit was greatest with the Quis lesion and equivalent for the Ib o and AMPA lesions. There was no deficit in single trial passive avoid ance retention for the Ibo and AMPA groups. The AMPA group was slower than controls on both training and retention trials to enter the dark compartment. This group also showed a tendency to hypoactivity as mea sured in an open-field test. Excitotoxic infusions into medial septum/ diagonal band and NBM produced spatial mnemonic deficits which do not parallel reductions in overall ChAT activity and do not resemble the p rofile of behavioral changes previously reported for NBM lesions alone using these toxins. (C) 1994 Academic Press, Inc.