Journal of Neuroscience, Vol 12, 3609-3618, Copyright © 1992 by Society for Neuroscience
Partial dopamine depletion of the prefrontal cortex leads to enhanced mesolimbic dopamine release elicited by repeated exposure to naturally reinforcing stimuli
JB Mitchell and A Gratton
Douglas Hospital Research Center, Department of Psychiatry, McGill University, Montreal, Quebec, Canada.
High-speed chronoamperometry was used to monitor the extracellular
concentration of dopamine within the nucleus accumbens, a terminal field of
the mesolimbic dopamine system, in freely behaving rats exposed daily, on 6
consecutive days, to one of two naturally reinforcing stimuli; a highly
palatable food or sex-related olfactory cues. The animals either were
intact or had previously received microinjections of 6-hydroxydopamine into
prefrontal cortex to lesion dopamine terminals. Food reliably elicited
increases in dopamine levels within the nucleus accumbens, and if
prefrontal cortical dopamine had been depleted, the response to food
increased with repeated testing. Animals exposed to the sexually relevant
olfactory stimulus showed progressively enhanced dopamine release with
repeated testing, and this enhancement was potentiated by prefrontal
cortical dopamine depletion. These results indicate that repeated exposure
to naturally reinforcing events can lead to a hyperresponsiveness of the
mesolimbic dopamine system upon future activation, and suggest that the
dopamine projection to prefrontal cortex exerts an indirect, inhibitory
influence on mesolimbic dopamine neurotransmission.