Injected muscimol in pedunculopontine tegmental nucleus alters ethanol self-administration

The pedunculopontine tegmental nucleus (PPN) has been implicated in a varie ty of behavioral functions, including stimulus selection. Given the PPN int eractions with the mesolimbic system, it was considered important to determ ine its involvement in ethanol self-administration. Long-Evans male rats we re trained to self-administer 10% ethanol by using a sucrose-substitution p rocedure. After implantation of cannula guides, microinjections of 30, 100, and 300 ng of muscimol into the PPN before the self-administration session were performed. Ethanol self-administration was decreased at the 300-ng do se, in a manner similar to the actions of dopamine agonists microinjected i n the nucleus accumbens. It is hypothesized that loss of PPN cholinergic in put to the mesolimbic system affects the integrative activity of the nucleu s accumbens and underlies the observed change in ethanol self-administratio n behavior. (C) 2001 Elsevier Science Inc. All rights reserved.