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Wednesday, September 26, 2007

Intra-median raphe nucleus (MRN) infusions of muscimol, a GABA-A receptor agonist, reinstate alcohol seeking in rats: role of impulsivity and reward
 Psychopharmacology Online First 22 September 2007


We previously found that the inhibition of median raphe nucleus (MRN) 5-HT transmission by local injections of a 5-HT1A agonist 8-OH-DPAT or corticotrophin-releasing factor (CRF) mimic the effect of foot shock stress to reinstate alcohol seeking.

In this study, we further explored the role of the MRN by examining the effect of inhibition of MRN neurons, by injecting the GABA-A receptor agonist muscimol, on the reinstatement of alcohol seeking.

MRN muscimol injections strongly reinstated alcohol seeking and this effect was not reversed by the depletion of 5-HT with 5,7-DHT. MRN muscimol injections did not induce a CPP, but did significantly impair multiple aspects of performance on the 5-CSRTT, including a marked increase in premature, or impulsive, responding.

Together with our previous findings, these results suggest that the inhibition of MRN projection neurons provokes alcohol seeking. Results from the 5-CSRTT suggest that increased impulsivity may contribute to these effects.

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