Effects of central endocannabinoid system on visceral hyposensitivity induced by rapid eye movement sleep deprivation: experiment with rats

Abstract

To study the effects and role of central endocannabinoid system in the mechanism of visceral hyposensitivity induced by rapid eye movement (REM) sleep deprivation. Twenty-four SD rat were divided randomly in to 3 groups: cage-yoked group (YC Group, experimental control group), REM sleep deprivation group (SD Group) exposed to REM sleep deprivation by means of flower pot technique lasting for 48 hours, and Rim Group, receiving rimonabant, a cannabinoid antagonist, after REM sleep deprivation. 48 hours after the sleep deprivation abdominal electromyogram in response to colorectal distension (CRD) was recorded to asses the visceral sensitivity. Then the rats were killed with their central nervous system taken out. RT-PCR and Western blotting were used to detect the RNA and protein expression of cannabinoid receptor CB1, fatty acid amide hydrolase (FAAH), and monoacylglycerol lipase (MGL) in the thalamus, brain stem, and spinal cord. (1) Under the pressures of 40, 60, and 80 mm Hg, the abdominal electrical activity frequencies of external oblique muscle responding to CRD in SD Group were (220 +/- 94), (313 +/- 162), and (493 +/- 279) times respectively, all significantly lower than those in YC Group [(506 +/- 223), (1053 +/- 548), and (1632 +/- 249) times respectively, all P < 0.05], and those of Rim Group were (668 +/- 257), (1144 +/- 93), and (1653 +/- 153) times respectively, all significantly higher than those of SD Group (all P < 0.05), but not significantly different from those of YC Group. (2) The RNA and protein expression levels of CB1 receptor in the thalamus, brain stem, and spinal cord of SD Group were all significantly higher than those of YC Group (all P < 0.05), while the RNA and protein expression levels of FAAH and MGL in the thalamus and spinal cord of SD Group were all significantly lower than those of YC Group (all P < 0.05). The visceral hyposensitivity induced by REM sleep deprivation may be associated with the increase of expression of CNS endocannabinoid receptor and decrease of its metabolism.