AREGU April 47/4

Ribeiro, Ana Cristina, John G. Gilligan, and Levente Kapás. Systemic injection of a nitric oxide synthase inhibitor suppresses sleep responses to sleep deprivation in rats. Am J Physiol Regulatory Integrative Comp Physiol 278: R1048– R1056, 2000.—We hypothesized that nitric oxide (NO) may play a role in homeostatic sleep regulation. To test this hypothesis, we studied the sleep deprivation (SD)-induced homeostatic sleep responses after intraperitoneal administration of an NO synthase inhibitor, Nv-nitro-L-arginine methyl ester (L-NAME, a cumulative dose of 100 mg/kg). Amounts and intensity of sleep were increased in response to 8 h of SD in control rats (n 5 8). Sleep amounts remained above baseline for 16 h after SD followed by a negative rebound. Rapid eye movement sleep (REMS) and non-REMS (NREMS) intensities were elevated for 16 and 4 h, respectively. LNAME treatment (n 5 8) suppressed the rebound increases in NREMS amount and intensity. REMS rebound was attenuated by L-NAME in the first dark period after SD; however, a second rebound appeared in the subsequent dark period. REMS intensity did not increase after SD in L-NAMEinjected rats. The finding that the NO synthase inhibitor suppressed rebound increases in NREMS suggests that NO may play a role as a signaling molecule in homeostatic regulation of NREMS.