Fig. 7.

Hypothetical framework for rapid eye movement (REM) sleep-dependent changes in heart rate. REM sleep-related activation of the LPGi neurons evokes GABAergic pathway to CVNs in the NA, which results in withdrawal of parasympathetic activity to the heart and increases in heart rate (right). H/H that typically occurs during apnea-associated events during REM sleep induces an α7 nicotinic receptor–mediated attenuation of the inhibitory pathway to parasympathetic CVNs that results in CVN disinhibition and activation of vagal tone, which may cause life-threatening bradyarrhythmias (left).