Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The nucleus accumbens (NA) receives inputs from limbic structures and projects to the basal ganglia. In addition, it is the target of a heavy dopaminergic projection from the ventral tegmental area (VTA). The purpose of the present study is to investigate using electrophysiological techniques whether or not the NA forms a functional link between the amygdala (AMY) and the ventral pallidum (VP), and whether or not the mesolimbic dopamine projection from the VTA interacts with this pathway.;Electrical stimulation of the basolateral nucleus of the AMY caused an excitation was attenuated by ionotophoretically applied dopamine (DA) or electrical stimulation of the VTA at 10 Hz for 1 s (VTA conditioning stimulation) prior to stimulation of the AMY. The attenuating effect of VTA conditioning stimulation was abolished by acute intraperitoneal injection of haloperidol, a DA antagonist, and was not observed in rats in which the mesolimbic DA projection had been lesioned by 6-hydroxydopamine.;Electrical stimulation of the AMY produced predominantly inhibitory responses in the VP. The onset latencies of the inhibitory responses showed a bimodal distribution suggesting that the responses could be elicited via two pathways. Those with long onset latencies (> 12 ms) were likely mediated via the NA since microinjection of procaine HCl or d-amphetamine into the NA abolished these responses. VTA conditioning stimulation also produced an attenuating effect on the long latency inhibitory responses in normal rats but not in rats with 6-OHDA lesions in the VTA. Inhibitory responses with short onset latencies (< = 12 ms) were not affected by any of these treatments.;These results suggest that the NA forms a connecting link between the AMY and the VP thus allowing output from the AMY to influence activity of neurons in the VP. Activity of the mesolimbic DA projection to the NA modulates the response of NA neurons to AMY input and thus the AMY's influence on the VP. Since the VP projects to motor areas of the brain, it is suggested that the AMY to NA to VP pathway may be a connecting link between the limbic and motor systems. The mesolimbic DA projection to the NA may serve as a "gate" to modulate output from limbic structures to the motor systems via this pathway.



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