Mechanisms contributing to the recovery of striatal releasable dopamine following MFB stimulation.

In vivo voltammetry was used to monitor the concentration of dopamine released into striatal extracellular fluid during electrical stimulation of the medial forebrain bundle of anesthetized rats. During stimulation the dopamine concentration increases rapidly to micromolar levels. After cessation of the stimulus, uptake mechanisms rapidly clear the released dopamine. That dopamine is the compound detected during stimulation is confirmed by voltammetry and pharmacology. The interval between stimulations influences the amount of dopamine released. When 10 s stimulations are spaced by 30 s, only 50% of the amount of dopamine released by the first stimulation is released by the second stimulation. Twenty minutes are required for full recovery of the stimulation response. Full recovery requires dopamine synthesis but during the initial 2 min following stimulation the recovery exceeds synthesis rates. Possible mechanisms that contribute to the rapid initial recovery are the mobilization of intraneuronally stored dopamine and the recycling of the released dopamine via presynaptic uptake mechanisms. Dopaminergic receptors are able to modulate the rapid recovery.