Abstract
Recent studies suggest that opioids can produce analgesia through peripheral mechanisms following inflammation of peripheral tissue. This study examined whether opioids administered prior to inflammation can produce antinociception by peripheral mechanisms in a model of visceral pain. Mice were injected intraperitoneally (i.p.) with 1% acetic acid to evoke abdominal writhing, a standard model of visceral pain. The number of writhes that occurred during 30 min after acetic acid were determined. Intraperitoneal injection of morphine sulfate (60, 90, 100 or 120 μg. 0.3 ml-1) or the peripherally acting opioid loperamide (0.12, 0.36, 1.2 or 3.6 mg.0.3 ml-1) given 5 min after acetic acid decreased writhing in a dose dependent fashion. Morphine (100 μg) produced an 70% attenuation in the number of writhes while loperamide (1.2 mg) decreased writhing by 56%. These antinociceptive effects were blocked by pretreatment with the opioid receptor antagonists naloxone (10 mg.kg-1) and its quarternary version naloxone methiodide (10 mg.kg-1). To determine whether opioids produced preemptive antinociception via peripheral mechanisms, mice received i.p. injections of morphine (1, 5, and 10 μg.0.3 ml-1) or vehicle 5 min before acetic acid. Doses of 5 and 10 μg morphine inhibited the number of writhes by 51 and 93%, respectively. The highest dose (10 μg) was ineffective when given intravenously 5 min before acetic acid, suggesting that antinociception following i.p. administration was acting via peripheral mechanisms. These data demonstrate that low doses of opioids, given before or after acetic acid, produce visceral antinociception through peripheral mechanisms. This may be clinically relevant for the management of postoperative abdominal pain.
Translated title of the contribution | Peripheral and preemptive opiod anticocieption in a mouse visceral pain model |
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Original language | Spanish |
Pages (from-to) | 423-431 |
Number of pages | 9 |
Journal | Revista de la Sociedad Espanola del Dolor |
Volume | 9 |
Issue number | 7 |
State | Published - Oct 2002 |
Bibliographical note
Funding Information:This work was supported by a grant from the Institute for Research and Education, Health System Minnesota (J.A.R.). We would like to thank Omodelle Masha for her assistance in earlier experiments. We are grateful to Drs Kenneth Hargreaves and Kumar Belani for critically reviewing an earlier version of the manuscript.
Keywords
- Opioid analgesia
- Peripheral
- Preemptive analgesia
- Visceral pain