Study Objectives: Serotonin, acting in the peripheral nervous system, can exacerbate sleep-related apnea, and systemically administered serotonin antagonists reduce sleep-disordered respiration in rats and bulldogs. Because cannabinoid receptor agonists are known to inhibit the excitatory effects of serotonin on nodose ganglion cells, we examined the effects of endogenous (oleamide) and exogenous (∆9-tetrahydrocannabinol; ∆9THC) cannabimimetic agents on sleep-related apnea. Design: Sleep architecture, respiratory pattern, and apnea expression in rats were assessed by polysomnography. A repeated measures, withinsubjects, fully nested crossover design was used in which each animal was recorded on exactly 12 occasions. Participants: Eleven adult male Sprague-Dawley rats were instrumented for chronic polysomnography. Interventions:...