Gonadal hormones decrease temporomandibular joint kappa-mediated antinociception through a down-regulation in the expression of kappa opioid receptors in the trigeminal ganglia.
We have previously demonstrated that activation of kappa-opioid receptor located in the temporomandibular joint (TMJ) of rats induces a significantly greater TMJ antinociception in diestrus females than in proestrus females (higher estradiol serum levels than diestrus) and males. These findings indicate that gonadal hormones decrease TMJ kappa-mediated antinociception. The aim of this study was to investigate some of the mechanisms by which gonadal hormones decrease TMJ kappa-mediated antinociception. Western blot analysis demonstrated a significantly lower kappa-opioid receptor expression in the trigeminal ganglia of intact males than in intact and ovariechtomized (OVX) females and orchidectomized (ORX) males. In females, kappa-opioid receptor expression in the trigeminal ganglia was significantly lower in proestrus than in diestrus and OVX females. Taken together these findings suggest that gonadal hormones, especially male gonadal hormones, down-regulate kappa-opioid receptor expression. Co-application of the NOS inhibitor L-NMMA or the NO-sensitive guanylyl cyclase inhibitor ODQ with the kappa-opioid receptor agonist U50,488 blocked TMJ kappa-mediated antinociception in males and females. These findings suggest that antinociception induced by activation of kappa opioid receptors in the TMJ region is mediated by the L-arginine/NO/cGMP pathway in both sexes. Despite the involvement of the L-arginine/NO/cGMP pathway in TMJ kappa-mediated antinociception in both sexes, gonadal hormones do not diminish the activity of this pathway to decrease TMJ kappa-mediated antinociception. Alternatively, they significantly reduce kappa-opioid receptor expression in the trigeminal ganglia.
Clemente-Napimoga
Juliana T
JT
Laboratory of Orofacial Pain, Department of Physiology, Piracicaba Dental School, State University of Campinas, Brazil; Laboratory of Biopathology and Molecular Biology, University of Uberaba, Brazil.
Pellegrini-da-Silva
Adriana
A
Ferreira
Vinícius H A
VH
Napimoga
Marcelo H
MH
Parada
Carlos A
CA
Tambeli
Cláudia H
CH
D000700:Analgesics / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001120:Arginine / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D005260:Female; D042341:Gonadal Hormones / Q000378:metabolism*; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D010146:Pain / Q000188:drug therapy / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000378:metabolism*; D012727:Sex Characteristics; D015398:Signal Transduction / Q000187:drug effects; D013704:Temporomandibular Joint / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism*; D019323:omega-N-Methylarginine / Q000494:pharmacology
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D000700:Analgesics; D042341:Gonadal Hormones; D010069:Oxadiazoles; D011810:Quinoxalines; D017473:Receptors, Opioid, kappa; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D006152:Cyclic GMP