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Thesis (M.S.)

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Amphetamines, Neurons


A larqe body of evidence supports the conclusion that mesolimbic dopaminerqic neurons, in particular those that innervate the nucleus accumbens (n.ACC), are important for the expression of d-amphetamine stimulated locomotor behavior (ASLB) . However, one recent study has contradicted this conclusion, reporting that bilateral lesions of the n.ACC fail to block ASLB. It appears that this study contains a methodoloqical flaw in that it employed a qeneral measure of activity which did not distinquish between locomotion and rcaring. In the present study, we used observer ratinqs of videotaped responses to determine the seperate effects of 2.0 mq/kq d-amphetamine on locomotion and rearinq in rats with either sham or radio-frequency lesions of the n.ACC. It was found that n.ACC lesiongs blocked the locomotor stimulation, but not the increased rearinq, which follows d-amphetamine administration. Additionally, the time spent engaging in stereotyped behaviors followinq administration of a hiqh dose of the donamine agonist apomorphine was not affected by the lesion. These results support the general conclusion that dooaminemic terminals in the n.ACC are important for the expression of ASLB, and further suggest that d-amnhetamine-stimulated locomotion and rearing are mediated throuoh different neural suibstrates.