In vitro demonstration of dopamine uptake by neostriatal serotonergic neurons of the rat.

Dopamine (DA) has been suggested as the penultimate agent in the neurotoxic effects of methamphetamine on serotonergic neurons. DA increases the efflux of tritium from rat neostriatal slices preloaded with [3H]serotonin in a concentration-dependent manner. This serotonin (5-HT) release is inhibited by the same selective uptake blockers previously shown to protect serotonergic neurons from the neurotoxic effects of methamphetamine in vivo. The results indicate that the 5-HT uptake carrier transports DA into the serotonergic neuron by a heteroexchange process with 5-HT. This further suggests that the excessive DA release induced by methamphetamine in vivo could lead to the uptake of DA into serotonergic neurons.