0309 Stress Induced Nitric Oxide Synthase Activation in the Basal Forebrain is a Result of Sleep Loss

Abstract Introduction The mechanisms underlying the reciprocal relationship between stress and sleep are unclear. Nitric oxide, a diffusible signaling molecule, plays an important role in physiological stress responses and sleep. The medial septum (MS) and vertical diagonal band (VDB) are sleep regulatory regions of the basal forebrain whose cells express nitric oxide synthase (NOS). In this study, we examined the effects of sleep loss and restraint stress on NOS activation in the MS and VDB. Methods Adult male and female C57BL/J6 mice were randomly assigned to a control, total sleep deprivation (TSD), or restraint stress group. TSD was performed for 6h using gentle handling, and restraint was performed for 6h by immobilizing the mice in a plastic restraint device. Both procedures began at light onset in a 12:12 light:dark cycle. Immediately following the procedures, mice were sacrificed, and NADPH-diaphorase (NADPH-d) was measured in the MS and VDB to determine NOS activity. Results A multivariate ANOVA revealed main effects of TSD and restraint stress on NADPH-d in the MS (F(2,13) = 7.0921, p = 0.011) and VDB (F(2,13)=6.416, p = 0.014) in females. A post hoc analysis showed a significant difference between control and TSD (p = 0.011 (MS), p = 0.014 (VDB)), and between control and restraint (p = 0.032 (MS), p = 0.048 (VDB)), but no significant difference between TSD and restraint. There is a sex difference in NADPH-d in these regions (p < 0.005) that reverses direction following TSD and restraint stress. Conclusion Our findings provide evidence that NOS activity in the basal forebrain may underlie sex differences in stress responses. Since there is no significant difference between the TSD and restraint stress, this suggests that the effect of restraint stress on NOS activation is a result of sleep loss, and not due to induction of a stress mechanism. Support This study was partly funded by R01-NS078410 and UCLA start-up funds.