Neuropeptide-Y Y2-receptor agonist, PYY3–36 promotes non-rapid eye movement sleep in rat

PYY3–36 is a major component of the gut–brain axis and peripheral administration has been reported to exert significant effects on feeding, brain function and is more selective for neuropeptide Y2 receptor. Therefore, we investigated the effects of nocturnal intraperitoneal administration of single doses of PYY3–36 (30 and 100 μg/kg i.p.) on food intake, water intake and the sleep–wake cycle in rats. Sleep recordings were carried out in male Sprague–Dawley rats implanted with cortical electroencephalogram (EEG) and neck electromyogram (EMG) electrodes. The EEG, EMG, food intake and water intake were assessed. The electrographic recordings obtained were scored visually as rapid eye movement (REM) sleep, non-REM (NREM) sleep and wakefulness.PYY3–36 administration 15 min prior to dark onset significantly (p < 0.05) increased non-rapid eye movement (NREM) sleep and decreased wakefulness. Analysis of the dark-period at 4-h time intervals showed that nocturnal administration of PYY3–36 (30 and 100 μg/kg) significantly suppressed wakefulness and increased non-REM sleep during the first 4-h time interval. Time spent in wakefulness was significantly decreased after administration of PYY3–36 (30 and 100 μg/kg) when compared with administration of vehicle. In addition, PYY3–36 (30 and 100 μg/kg i.p.) induced an increase in the time spent in NREM sleep. The nocturnal intraperitoneal administration of the lower dose of PYY3–36 (30 μg/kg) also significantly decreased food intake [F (2,23) = 4.90, p < 0.05] but had no effect on water intake. These findings suggest that PYY3–36 may play an important role in the enhancement of NREM sleep and feeding behavior.