Sánchez, EvaBagues, AnaMartin, Mª Isabel2024-07-262024-07-262010Eva M Sánchez, Ana Bagües, M Isabel Martín, Contributions of peripheral and central opioid receptors to antinociception in rat muscle pain models, Pharmacology Biochemistry and Behavior, Volume 96, Issue 4, 2010, Pages 488-495, ISSN 0091-3057, https://doi.org/10.1016/j.pbb.2010.07.009https://hdl.handle.net/10115/38870This work was supported by a grant from the Ministry of Education and Science of Spain ( SAF2006-13391-C03-01 ). A. Bagües is a research fellow from the Ministry of Education and Science. The authors like to thank Carmen Merino for technical assistance. There is no conflict of interest associated with this manuscript.Administration of hypertonic saline (HS) is an accepted model to study muscular pain. HS-induced nociceptive responses were tested in masseter, already described, and in two new pain models of spinally innervated muscles (gastrocnemius and triceps) developed in rats at our laboratory. HS administration in the masseter induced vigorous hindpaw shaking and in the gastrocnemius or triceps, paw withdrawal or flexing. Participation of the central and peripheral opioid receptors in HS-induced pain is compared in these muscles: masseter, innervated by trigeminal nerve, and gastrocnemius and triceps by spinal nerves. Morphine and loperamide were used to reveal peripheral and central components of opioid analgesia. Both agonists reduced HS-induced nociceptive behaviours in the masseter and were antagonised by the opioid antagonist naloxone and by naloxone methiodide, an opioid receptor antagonist that poorly penetrates the blood–brain barrier. Unexpectedly, in the gastrocnemius and triceps, morphine, but not loperamide, decreased the nociceptive behaviour and this effect was only reversed by naloxone. So, peripheral opioid receptors seem to participate in HS-induced masseter pain, whereas only central opioid receptors reduced the nociception in gastrocnemius and triceps. Our results suggest that the use of peripheral opioids can be more advantageous than central opioids for treatment of orofacial muscular pain.engMuscular painMasseterGastrocnemiusHypertonic salineOpioidTricepsinfo:eu-repo/semantics/article10.1016/j.pbb.2010.07.009info:eu-repo/semantics/closedAccess