Korean J Anesthesiol.  2012 Jan;62(1):66-72. 10.4097/kjae.2012.62.1.66.

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

Affiliations
  • 1Department of Anesthesia and Pain Medicine, Pusan National University School of Medicine, Busan, Korea. hakykim@pusan.ac.kr
  • 2Department of Anesthesia and Pain Medicine, Pusan National University School of Dentistry, Busan, Korea.

Abstract

BACKGROUND
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.
METHODS
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).
RESULTS
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.
CONCLUSIONS
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.

Keyword

Ketamine; Mechanical allodynia; Morphine; Paclitaxel; Rat; Sex differences

MeSH Terms

Analgesics
Animals
Female
Humans
Hyperalgesia
Injections, Intraperitoneal
Ketamine
Male
Morphine
Neuralgia
Paclitaxel
Rats
Rats, Sprague-Dawley
Sex Characteristics
Analgesics
Ketamine
Morphine
Paclitaxel
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