COMPARISON OF DOPAMINE UPTAKE IN THE BASOLATERAL AMYGDALOID NUCLEUS, CAUDATE-PUTAMEN, AND NUCLEUS-ACCUMBENS OF THE RAT

Regional differences in the kinetics and pharmacological inhibition of dopamine uptake were investigated with fast-scan cyclic voltammetry i n both the intact rat brain and a brain slice preparation. The regions compared were the basolateral amygdaloid nucleus, caudate-putamen, an d nucleus accumbens. The frequency dependence of dopamine efflux evoke d in vivo by electrical stimulation of the medial forebrain bundle was evaluated by nonlinear curve fitting with a Michaelis-Menten-based ki netic model. The K-m for dopamine uptake was found to be significantly higher in the basolateral amygdala (0.6 mu M) than in the other two r egions (0.2 mu M), whereas the V-max value for dopamine uptake in the basolateral amygdala was significantly lower (0.49 mu M/s vs. 3.8 and 2.4 mu M/s in the caudate and accumbens, respectively). Similar kineti cs were also obtained in brain slices. Addition of a dopamine uptake i nhibitor, cocaine or nomifensine (10 mu M), to the perfusion buffer in creased the apparent K-m value > 25-fold in slices of both the caudate -putamen and nucleus accumbens. In contrast, neither uptake inhibitor had an observable effect in the basolateral amygdaloid nucleus. Thus, dopamine uptake in the rat brain is regionally distinct with regard to rate, affinity, and sensitivity to competitive inhibition.