Estrogen-dependent, sex-specific modulation of mustard oil-induced secondary thermal hyperalgesia by orphanin FQ in the rat.
Activation of opioid receptor-like 1 receptor (ORL(1)) by intrathecal administration of orphanin FQ (OFQ), an endogenous ligand for the ORL(1) receptor, has been shown to produce antinociception. In addition, we have recently shown gonadal hormone-dependent, sex-specific modulation of acute spinal nociception such that estrogen attenuated OFQ-induced antinociception in the female whereas testosterone was required for the expression of antinociception in the male. However, sex-related differences in the role of OFQ under hyperalgesic conditions are unknown. Hence, we investigated whether OFQ produces sex-specific modulation of mustard oil-induced secondary thermal hyperalgesia in the rat. Mustard oil application to the hind limb significantly reduced the tail-flick latencies (TFL) in male, and ovariectomized (OVX), estradiol treated ovariectomized (OVX+E), proestrous (ProE) and diestrous (DiE) females. Intrathecal administration of OFQ not only attenuated mustard oil-induced decrease in TFLs, i.e. reversed hyperalgesia, but also led to a significant increase in TFLs above the baseline, i.e. produced antinociception in male, OVX, and diestrous rats. However, OFQ failed to alter TFLs in proestrous or OVX+E females, thus these two groups with elevated estrogen levels remained hyperalgesic following mustard oil treatment. These findings demonstrate that OFQ modulates mustard oil-induced secondary hyperalgesia in an estrogen-dependent, sex-specific manner.
Department of Neurobiology & Neurotoxicology, Meharry Medical College, Nashville, TN 37208, USA.
Jomo A
JA
Claiborne
Subodh
S
Nag
Sukhbir S
SS
Mokha
D000818:Animals; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism*; D007509:Irritants / Q000633:toxicity; D008297:Male; D009149:Mustard Plant / Q000633:toxicity; D018847:Opioid Peptides / Q000378:metabolism* / Q000494:pharmacology; D010052:Ovariectomy; D010146:Pain / Q000378:metabolism*; D017288:Pain Threshold / Q000187:drug effects; D010938:Plant Oils / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000378:metabolism; D012727:Sex Characteristics; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D004967:Estrogens; D007509:Irritants; D018847:Opioid Peptides; D010938:Plant Oils; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C027793:mustard oil