Striatal dopamine dynamics are altered following an intranigral infusion of iron in adult rats

In vivo electrochemical detection was employed to examine iron-induced oxidative injury on dopamine dynamics in the nigrostriatal system of urethane-anesthetized rats. Seven days after an intranigral infusion of iron, oxidative stress was confirmed by an elevated lipid peroxidation in lesioned substantia nigra (SN). Local application of potassium (K⁺) evoked dopamine releases from the dopamine-containing nerve terminals in the striatum. Both amplitude and rate of clearance (Tc) of evoked dopamine releases were lower in striatum with lesioned SN; however, the time course parameters of dopamine release in the lesioned group were not different from those of the intact group, indicating a reduction in dopamine clearance. Indeed, iron-induced oxidative stress attenuated the effect of nomifensine, a high-affinity dopamine uptake blocker, on dopamine clearance. In striatum with intact SN, the amplitude and time course parameters of signals by exogenous dopamine were increased and Tc was decreased by nomifensine. In contrast, nomifensine did not significantly alter the dopamine signals of the lesioned group. Taken together, in addition to the increased lipid peroxidation in SN, our in vivo electrochemical data demonstrates that iron-induced oxidative injury attenuates K⁺-evoked dopamine release and dopamine uptake in the ipsilateral striatum. The diminished nomifensine effect implies a lack of high-affinity dopamine uptake sites.