Experimental neurology
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Experimental neurology · Jan 2012
Sexual dimorphism in endothelin-1 induced mechanical hyperalgesia in the rat.
While the onset of mechanical hyperalgesia induced by endothelin-1 was delayed in female rats, compared to males, the duration was much longer. Given that the repeated test stimulus used to assess nociceptive threshold enhances hyperalgesia, a phenomenon we have referred to as stimulus-induced enhancement of hyperalgesia, we also evaluated for sexual dimorphism in the impact of repeated application of the mechanical test stimulus on endothelin-1 hyperalgesia. In male and female rats, endothelin-1 induced hyperalgesia is already maximal at 30 min. ⋯ In contrast, in females, it develops only after a very long (15 day) delay, and is still present, without attenuation, at 45 days. Ovariectomy eliminated these differences between male and female rats. These findings suggest marked, ovarian-dependent sexual dimorphism in endothelin-1 induced mechanical hyperalgesia and its enhancement by repeated mechanical stimulation.