title: Nitric oxide modulates the hyperalgesic response to mechanical noxious stimuli in sleep-deprived rats.
abstract: BACKGROUND
  Sleep restriction alters pain perception in animals and humans, and many studies have indicated that paradoxical sleep deprivation (PSD) promotes hyperalgesia. The hyperalgesia observed after mechanical nociceptive stimulus is reversed through nitric oxide synthase (NOS) inhibition. Both nitric oxide (NO) and the dorsolateral periaqueductal gray matter (dlPAG) area of the brainstem are involved in hyperalgesia. Thus, in this work, we investigated the pain-related behavior response after mechanical noxious stimuli (electronic von Frey test), and the activity of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), an indicator of NOS activity, within the dlPAG of paradoxical sleep-deprived rats. We also evaluated the effects of pre-treatment with L-NAME on these parameters.
  
  
  RESULTS
  These data revealed that PSD reduced the hindpaw withdrawal threshold (-47%, p < 0.0001) confirming the hyperalgesic effect of this condition. In addition, there were more NADPH-d positive cells in dlPAG after PSD than in control rats (+ 59%, p < 0.0001). L-NAME treatment prevented the reduction in the hindpaw withdrawal threshold (+ 93%, p < 0.0001) and the increase in the NADPH-d positive cells number in the dlPAG of PSD-treated rats (-36%, p < 0.0001).
  
  
  CONCLUSIONS
  These data suggest that the hyperalgesic response to mechanical noxious stimuli in paradoxical sleep-deprived rats is associated with increased NOS activity in the dlPAG, which presumably influences the descending antinociceptive pathway.
authors.affiliation: Department of Pharmacology and Psychobiology, Institute of Biology, State University of Rio de Janeiro, Av, 28 de Setembro, 87-Fundos, 20551-030, Rio de Janeiro, Brazil. olgafarmaco@gmail.com.
authors.forename: Fabio
authors.initials: F
authors.lastname: Damasceno
authors.forename: Gabriela O
authors.initials: GO
authors.lastname: Skinner
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Araújo
authors.forename: Marcia M D
authors.initials: MM
authors.lastname: Ferraz
authors.forename: Frank
authors.initials: F
authors.lastname: Tenório
authors.forename: Olga M M S
authors.initials: OM
authors.lastname: de Almeida
mesh_terms: D000818:Animals; D006930:Hyperalgesia / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D010487:Periaqueductal Gray / Q000378:metabolism*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D012892:Sleep Deprivation / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide