Vasoactive intestinal polypeptide induces REM recovery in insomniac forebrain lesioned cats

Basal forebrain (BF) lesions in cats produces insomnia by reducing both slow wave sleep (SWS) and rapid-eye-movement (REM) sleep time. Recently it has been shown that vasoactive intestinal polypeptide (VIP) may be a specific REM inductor in the parachlorophenylalanine (PCPA) insomniac model. The purpose of this study was to test the hypnogenic properties of VIP in a nonpharmacological model of insomnia. Cats were rendered insomniac by delivering a DC current through stainless steel tripolar electrodes implanted in the basal forebrain area (BFA). Sleep-waking cycle recordings were done prior to lesions and on days 7, 9, 10, 11, 14, and 21 days after BF lesion. On day 10 after the lesion, 200 ng of VIP was injected into the 4th ventricle. Results showed that on postlesion days 7 and 9, SWS and REM sleep total times decreased, while waking time increased significantly. VIP restored REM sleep total time and frequency for almost 48 h, and SWS sleep total time for 24 h. On days 14 and 21 postlesion, insomnia was reestablished. Results are discussed in terms of the possible anatomical and neurochemical substrates whereby VIP can induce the recovery of sleep-waking control values.