Brain research bulletin
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Brain research bulletin · Oct 2007
DAMGO and 6beta-glycine substituted 14-O-methyloxymorphone but not morphine show peripheral, preemptive antinociception after systemic administration in a mouse visceral pain model and high intrinsic efficacy in the isolated rat vas deferens.
Peripheral micro-opioid receptors (MOR) have emerged as important components of inhibitory nociceptive pathways. Here, the antinociceptive effects of MOR agonists, the 6beta-glycine derivative of 14-O-methyloxymorphone (HS-731), DAMGO and morphine were evaluated in a mouse model of visceral pain. The abdominal acetic acid-induced writhing test was used to examine the peripheral, preemptive antinociceptive opioid action on visceral nociception. ⋯ These data demonstrate that selective activation of peripheral MOR by systemic s.c. HS-731 or DAMGO produces potent peripheral, preemptive visceral antinociception, while morphine's effects are mediated primarily through central mechanisms. Our findings support the role of peripheral MOR in the pathology of pain states involving sensitization of peripheral nociceptors.