Role of medial prefrontal, entorhinal, and occipital 5-HT in cocaine-induced place preference and hyperlocomotion: evidence for multiple dissociations |
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Authors: | M E Pum R J Carey J P Huston C P Müller |
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Institution: | Institute of Physiological Psychology, University of Düsseldorf, Düsseldorf, Germany. |
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Abstract: | Rationale Application of cocaine or exposure to cocaine-related stimuli induces widespread activation of the cortex in neuroimaging
studies with human subjects. In accordance to these findings, it was reported in previous microdialysis experiments that cocaine
increased serotonin (5-HT) and dopamine in various cortical brain areas. The present series of studies set out to investigate
the functional role of the observed increases in 5-HT in the medial prefrontal cortex (mPFC), the entorhinal cortex (EC),
and the occipital cortex (OccC) in the mediation of cocaine-induced conditioned place preference (CPP) and hyperactivity.
Materials and methods To reduce 5-HTergic neurotransmission in circumscribed brain areas, bilateral local infusions of the serotonergic neurotoxin,
5,7-dihydroxytryptamine (5,7-DHT), were made into the mPFC, EC, or OccC. Two weeks following surgery, cocaine-induced (10 mg/kg;
i.p.) CPP was measured in an unbiased design.
Results The 90% depletion of 5-HT in the mPFC significantly attenuated the preference for the cocaine-associated environment and the
hyperlocomotor response to cocaine. A 61% depletion of 5-HT in the EC reduced conditioned place preference without modulation
of hyperactivity, while a 78% 5-HT depletion of the OccC cortex had no effect on cocaine-induced CPP and hyperactivity. No
lesion affected general activity, habituation learning, or visual stimulation-induced behavioral activation.
Conclusion These results indicate an important role of cortical 5-HT in the mediation of cocaine-induced CPP and specify the region-dependent
contribution of a neurochemical response to cocaine-mediated behavior. |
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Keywords: | Cocaine Serotonin Cortex Conditioned place preference 5 7-Dihydroxytryptamine |
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