TRH-induced antinociception: interaction with the opioid systems?
Mice were chronically treated with morphine or ethylketocyclazocine in order to induce a marked tolerance to their antinociceptive effect in the phenyl-p-benzoquinone writhing test. TRH (2 mg kg-1 i.p.) significantly reduced the number of writhes in non-tolerant mice, but did not alter the response of morphine- or ethylketocyclazocine-tolerant mice. TRH did not modify the binding of [3H]naloxone in mouse brain either in vitro (TRH: 10(-10)-10(-4) M) or ex vivo (TRH: 1-40 mg kg-1 i.p.). There was no dose-dependent modification of the in vivo binding of [3H]lofentanil in any of the mouse brain areas studied after TRH (1-40 mg kg-1 i.p.).
D000698:Analgesia; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D003496:Cyclazocine / Q000031:analogs & derivatives / Q000494:pharmacology; D004723:Endorphins / Q000502:physiology*; D016314:Ethylketocyclazocine; D005283:Fentanyl / Q000031:analogs & derivatives / Q000378:metabolism; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000378:metabolism; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D004723:Endorphins; D011957:Receptors, Opioid; D009270:Naloxone; D016314:Ethylketocyclazocine; D013973:Thyrotropin-Releasing Hormone; D009020:Morphine; C034846:lofentanil; D003496:Cyclazocine; D005283:Fentanyl