首页|Investigation on the relationship between cannabinoid CB_1 and opioid receptors in gastrointestinal motility in mice
Investigation on the relationship between cannabinoid CB_1 and opioid receptors in gastrointestinal motility in mice
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1 This study investigated whether (a) cannabinoid CB_1 receptor knockout (CB_1~(-/-)) mice displayed altered gastrointestinal transit and (b) cannabinoid CB_1 and opioid receptors functionally interact in the regulation of gastrointestinal transit. 2 Gastrointestinal transit was assessed by the Whole Gastrointestinal Transit, measuring the excretion time of an intragastrically administered marker (whole intestine), and the Upper Gastrointestinal Transit, measuring the distance covered by the marker in the small intestine. 3 CB_1~(-/-) and homozygous CB_1~(+/+) (CB_1~(+/+)) mice did not differ in both whole gut and small intestine transit. CB_1~(-/-) and CB_1~(+/+) mice were equally responsive to the inhibitory effect of morphine (10 mg kg~(-1)) and loperamide (3 mg kg~(-1)) on whole gut transit. 4 Additionally, in CD1 mice the cannabinoid CB_1 receptor antagonist, rimonabant (0-0.5 mg kg~(-1)), failed to block the inhibitory effect of morphine (0-1.25 mg kg~(-1)) and loperamide (0-0.5 mg kg~(-1)) on transit in small and whole intestine. Similarly, the opioid receptor antagonists, naloxone (0-1 mg kg~(-1)) and naltrexone (0-10 mg kg~(-1)), failed to block the inhibitory effect of the cannabinoid WIN 55,212-2 (0-3 mg kg~(-1)) on transit in small and whole intestine. 5 These results suggest that (a) compensatory mechanisms likely developed in CB_1~(-/-) mice to overcome the lack of inhibitory function of endocannabinoid system; (b) cannabinoid and opioid receptor systems did not interact in regulating gastrointestinal transit in mice.
NETL
NSTL
