The Pronociceptive Effect of Paradoxical Sleep Deprivation in Rats: Evidence for a Role of Descending Pain Modulation Mechanisms.

The mechanisms underlying the pronociceptive effect of paradoxical sleep deprivation (PSD) are not known. In this study, we asked whether PSD increases tonic nociception in the formalin test, decreases the antinociceptive effect of morphine administered into the periaqueductal gray matter (PAG), and disrupts endogenous descending pain modulation. PSD for either 24 or 48 h significantly increased formalin-induced nociception and decreased mechanical nociceptive paw withdrawal threshold.