Long-lasting enhancement of rapid eye movement sleep and pontogeniculooccipital waves by vasoactive intestinal peptide microinjection into the amygdala temporal lobe

Abstract

Study Objectives: The effect of a vasoactive intestinal peptide (VIP) microinjection into the amygdaloid central (CN) and basal nuclei (BN) on sleep organization and on the number and pattern of occurrence of pontogeniculooccipital (PGO) waves was analyzed. Design: One group of 8 cats was studied in baseline conditions and after the microinjection of two doses of VIP applied into the CN and BN. Setting: Sleep research laboratory. Participants and Interventions: Eight cats were prepared with sleep-recording electrodes and with guide tubes in both amygdalae for saline and VIP microinjections. Neuropeptide doses of 0.10mug/1mul (30muM) and 0.33mug/1mu1 (99.24muM) were employed. Measurements and Results: Once the microinjection was applied, 23-hour polygraphic sleep recordings were performed for 5 consecutive days. Concomitantly the PGO waves were tape-recorded on each day and computationally analyzed. Results show that the 0.10mug/1mul microinjection produced no change. Unilateral VIP 0.33mug/1mul injection into the CN provoked a significant and lasting increase in the percentage of slow-wave sleep with PGO waves. Bilateral application of VIP increased the percentage of slow-wave sleep with PGO waves and rapid eye movement sleep for 5 days. Bilateral microinjection of the neuropeptide into the BN only enhanced the percentage of slow wave sleep with PGO waves. For both amygdaloid nuclei, we observed that VIP increased the number and modified the PGO wave pattern of occurrence during slow-wave sleep with PGO waves and during rapid eye movement sleep. Conclusions: The VIP microinjection into both the CN and BN induces increased amounts of rapid eye movement sleep, PGO waves, and slow-wave sleep with PGO waves, having a more robust effect on all of these three variables when applied into the CN.