Gender differences in paclitaxel-induced neuropathic pain behavior and analgesic response in rats

• Published in: Korean journal of anesthesiology Vol. 62; no. 1; pp. 66 - 72
• Main Authors: Hwang, Boo-Young, Kim, Eun-Soo, Kim, Chul-Hong, Kwon, Jae-Young, Kim, Hae-Kyu
• Format: Journal Article
• Language: English
• Published: Korea (South) The Korean Society of Anesthesiologists 2012; Korean Society of Anesthesiologists; 대한마취통증의학회
• Subjects: Experimental; ketamine; mechanical allodynia; morphine; paclitaxel; rat; sex differences; 마취과학; Morphine; Sex differences; Ketamine; Rat; Paclitaxel; Mechanical allodynia
• ISSN: 2005-6419; 2005-7563; 2005-7563
• DOI: 10.4097/kjae.2012.62.1.66

Females show greater sensitivity than males to several modalities of experimental pain. However, the gender differences in paclitaxel-induced neuropathic pain have not been studied. The current study examined the gender differences in neuropathic pain behavior and the effect of analgesics in a paclitaxel-induced neuropathic pain model in rats. Neuropathic pain was induced by intraperitoneal injection of paclitaxel (2 mg/kg) on 4 alternate days in Sprague-Dawley rats of both genders. Mechanical allodynia was measured using a von Frey filament. The gender differences in analgesic responses were determined after administration of morphine (2 or 5 mg/kg), ketamine (2 or 5 mg/kg), or combined morphine (2 mg/kg) and ketamine (2 mg/kg). Paclitaxel induced mechanical allodynia, which began to manifest on day 4, peaked within 10 days, and plateaued for at least 2 months after the first paclitaxel injection. No gender difference in the manifestation of mechanical allodynia was observed. A 2 mg/kg dose of ketamine increased the mechanical threshold only in males. The 5 mg/kg dose of ketamine significantly increased the mechanical threshold in both genders. Morphine (2 and 5 mg/kg) dose-dependently increased the mechanical thresholds in both genders. The 2 mg/kg dose of ketamine enhanced the antinociceptive effect of 2 mg/kg morphine only in females. No gender difference in paclitaxel-induced neuropathic pain or analgesic response to ketamine or morphine was observed in Sprague-Dawley rats. Low dose ketamine enhanced the analgesic effect of morphine on paclitaxel-induced mechanical allodynia but only in female rats.