TY - JOUR T1 - Body Temperature and Analgesic Effects of Selective <em>Mu</em>and <em>Kappa</em> Opioid Receptor Agonists Microdialyzed into Rat Brain JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 499 LP - 507 VL - 281 IS - 1 AU - Li Xin AU - Ellen B. Geller AU - Martin W. Adler Y1 - 1997/04/01 UR - http://jpet.aspetjournals.org/content/281/1/499.abstract N2 - Opioids administered by i.c.v. injection produce body temperature (Tb) changes and analgesic responses in rats. The present study was undertaken to investigate the effects on Tb and analgesia of highly selective mu and kappa opioid receptor agonists and antagonists delivered directly into the preoptic anterior hypothalamus (POAH) and periaqueductal gray (PAG) by the intracerebral microdialysis method. Microdialyzed into the POAH, themu receptor agonist Tyr-Pro-N-MePhe-D-Pro-NH2induced dose-related hyperthermia that could be prevented or antagonized by the mu receptor antagonist cyclic D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 or by naloxone, but not by the kappa receptor antagonist nor-binaltorphimine. The kappa receptor agonist dynorphin A1–17, microdialyzed into the POAH, induced dose-related hypothermia that was prevented or antagonized by nor-binaltorphimine but not cyclic D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2. Neither Tyr-Pro-N-MePhe-D-Pro-NH2 nor dynorphin A1–17microdialyzed into the PAG produced significant changes in Tb. However, these agonists microdialyzed into the PAG produced analgesic responses that did not occur after administration into the POAH. These results support the hypothesis that the hyperthermic response to opioids is mediated by the mu receptor and the hypothermic response is mediated by the kappa receptor in rats. The POAH is a primary functional area in Tb, but not in analgesic, responses to opioids, whereas the PAG is a sensitive area for analgesic, but not for Tb, responses to opioids. The American Society for Pharmacology and Experimental Therapeutics ER -