Microinjecting cholinomimetics into the medial pontine reticular formation (mPRF) of conscious cats causes a rapid eye movement (REM) sleep-like state and state-dependent respiratory depression. Muscarinic receptors within the mPRF have been shown to mediate this state-dependent respiratory depression, but the specific signal transduction mechanisms remain poorly understood. This study tested the hypothesis that the cholinergically induced REM sleep-like state and state-dependent respiratory depression are mediated by guanine nucleotide binding proteins (G proteins). Cholera toxin, pertussis toxin, 5'-guanylylimidodiphosphate, and forskolin were microinjected alone and in combination with carbachol into the mPRF of intact unanesthetized cats. All of the G protein-altering compounds significantly reduced the ability of carbachol to produce the REM sleep-like state. Pertussis toxin caused the greatest decrease in the percent of time spent in the carbachol-evoked REM sleep-like state, showing for the first time mediation by a pertussis toxin-sensitive (Gi- or G(o)-like) G protein. Cholera toxin blocked the carbachol-induced respiratory depression, indicating mediation by a Gs-like G protein. Forskolin significantly decreased carbachol-evoked REM sleep. These data provide the first demonstration that adenylyl cyclase within the mPRF contributes to the carbachol induction of REM sleep and respiratory depression.