CHOLINERGIC BLOCKADE AND LESIONS IN VENTRO-MEDIAL SEPTUM OF RAT

Small lesions of the ventro-medial septum of rats increased spontaneous locomotor activity and reactivity to light and facilitated the acquisition as well as the reversal of shuttle-box avoidance responses. Food and water intake were not significantly modified. There was no evidence of perseverative responding during CAR reversal acquisition. The application of small doses (2-5 μg) of atropine methyl nitrate to the same region did not produce significant changes in reactivity to photic stimuli but facilitated CAR acquisition. Repeated injections of high doses (4-7 μg) of atropine facilitated CAR acquisition when rats were required to respond to light (CS) onset but not when they were required to respond to its offset. Neither dose of atropine caused a significant change in spontaneous activity or produced evidence of perseverative responding during CAR reversal acquisition. Both doses of atropine resulted in an initial depression of food and water intake. These results indicate that dysfunctions underlying changes in locomotor activity and reactivity to light do not mediate two-way CAR facilitation and suggest further that there is a cholinergic system within the septum whose disruption has a direct facilitatory effect on the acquisition of a two-way CAR. © 1969.