THE EFFECTS OF LIMBIC LESIONS ON LOCOMOTION AND STEREOTYPY ELICITED BY DOPAMINE AGONISTS IN THE RAT

The purpose of this experiment was to investigate the functional contr ibutions of various limbic structures to locomotion and stereotypy ind uced by dopaminergic drugs. Female rats were randomly assigned to one of 5 groups (n=10-14 rats/group) that received either a lesion of the hippocampus (colchicine + kainic acid), basolateral amygdala (quinolin ic acid), frontal cortex (aspiration), nucleus accumbens (ibotenic aci d), or served as unoperated controls. Beginning at least 2 weeks follo wing surgery locomotion (measured as photocell beam breaks) elicited b y D-amphetamine (0.0, 0.32, 1.0 and 3.2 mg/kg), SKF 82958 (0.0, 0.04, 0.08 and 0.16 mg/kg) or quinpirole (0.0, 0.25, 0.1 and 0.5 mg/kg) was determined. In agreement with previous results rats with hippocampal l esions were hyperactive in response to amphetamine. In comparison to t hese changes in drug-induced locomotion, lesions of the basolateral am ygdala, and frontal cortex had only minor effects on drug-induced loco motion. Lesions of the nucleus accumbens produced consistent hyperacti vity that was suppressed by doses of amphetamine or quinpirole that el icited behavioral stereotypy. These results provide evidence suggestin g that, in comparison to other limbic structures that have substantial inputs to the nucleus accumbens, the hippocampus play a relatively pr ominent role in the modualtion of drug-induced locomotion.