Korean J Pain.  2005 Dec;18(2):113-117. 10.3344/kjp.2005.18.2.113.

Assessment for the Role of Serotonin Receptor Subtype 3 for the Analgesic Action of Morphine at the Spinal Level

• Yoon MH
• Bae HB
• Choi JI
• Kim SJ
• Kim CM
• Jeong ST
• Kim KS
• Jin WJ
• Kim JP
• Kim JS
• Kim SY
• Jeong CY

• KMID: 2277972
• DOI: http://doi.org/10.3344/kjp.2005.18.2.113

Abstract

BACKGROUND
Serotonin 3 receptor is involved in the modulation of nociceptive transmission in the spinal cord. The serotonin 3 receptor antagonist has been used for the management of opioid-induced nausea and vomiting. The aim of this study was to examine whether the analgesic effect of morphine is antagonized by serotonin 3 receptor antagonists at the spinal level. METHODS: Rats were implanted with lumbar intrathecal catheters. For nociception, a formalin solution (5%, 50microliter) was injected into the hind paw of male Sprague-Dawley rats. To determine whether the effect of intrathecal morphine was mediated via serotonin 3 receptors, serotonin 3 receptor antagonists were intrathecally administered 10 min prior to the morphine delivery. Following the formalin injection, formalin-induced nociceptive behavior (flinching response) was observed for 60 min. RESULTS: Intrathecal morphine produced a dose-dependent suppression of the flinches in both phases during the formalin test. The analgesic action of morphine was not reversed by serotonin 3 receptor antagonists (LY-278, 584, ondansetron), which had little per se effect on the formalin-induced nociception. CONCLUSIONS: Spinal serotonin 3 receptors may not be involved in the analgesia of morphine on a nociceptive state evoked by a formalin stimulus.

Keyword

analgesia; formalin test; morphine; rat; serotonin 3 receptor; spinal cord

MeSH Terms

Analgesia
Animals
Catheters
Formaldehyde
Humans
Male
Morphine*
Nausea
Nociception
Pain Measurement
Rats
Rats, Sprague-Dawley
Receptors, Serotonin, 5-HT3
Serotonin*
Spinal Cord
Vomiting
Formaldehyde
Morphine
Receptors, Serotonin, 5-HT3
Serotonin