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.