The Cardioacceleratory Response to Arecoline Infusion During Sleep in Narcoleptic Subjects and Controls

Nine narcoleptic and nine control subjects underwent 4 nights of sleep recordings. On nights 3 and 4, they received continuous intravenous infusions of saline. Additionally, on both nights they received 0.2 mg glycopyrrolate at the end of the first REM period (REM1) and 0.5 mg arecoline or placebo in random order 20 min after the end of REM1. Heart rates were counted for a 40-min period following the end of REM1. There was a significant and similar cardioacceleratory effect after arecoline in both narcoleptic and normal subjects, beginning at 5 min from the start of the infusion and peaking at 9 min. Placebo had no effect. Narcoleptic subjects had consistently higher baseline heart rates than controls on infusion and noninfusion nights, most likely owing to age differences between the two groups. The results suggest that narcoleptic persons do not have increased cholinergic sensitivity, or that the canine model of narcolepsy differs from the human model, or that the muscarinic receptors that play a role in the pathophysiology of narcolepsy differ in sensitivity from those that regulate heart rate.