title: Tolerance and inverse tolerance to the hyperalgesic and analgesic actions, respectively, of the novel analgesic, F 13640.
abstract: 5-HT(1A) receptor activation by the very-high-efficacy, selective 5-HT(1A) receptor agonist F 13640 [(3-Chloro-4-fluoro-phenyl)-[4-fluoro-4-([(5-methyl-pyridin-2-ylmethyl)-amino]-methyl)piperidin-1-yl]-methanone] was recently discovered to constitute a novel central mechanism of broad-spectrum analgesia that, remarkably, grows rather than decays with chronicity. However, in rodents not exposed to nociception, F 13640 induces its analgesic effect only after having initially induced hyperalgesia. Numerical simulations implementing a signal transduction theory here show that the progressive increase in the intensity of nociceptive stimulation which F 13640 presumably mimics should eventually produce a large analgesic effect without initially causing marked pain. In vivo studies examined the effects of progressively increasing doses of F 13640 on the threshold of mechanically induced vocalization and, also, on the 5-HT syndrome in rats. The infusion of increasing (0.04-0.63 mg/rat/day) doses of F 13640 over a 5-week period induced a large analgesia preceded by a hyperalgesic effect that was small and comparable to that induced by initial exposure to a low, 0.04 mg/rat/day dose. Furthermore, increasing the dose of F 13640 induced tachyphylaxis to the 5-HT syndrome. Producing the mirror opposite of morphine's neuroadaptive actions, F 13640 causes an analgesia that becomes more powerful with chronic administration, and this at the expense of the initial hyperalgesia which it may also produce.
authors.affiliation: Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, 81106 Castres Cedex, France.
authors.forename: Liesbeth A
authors.initials: LA
authors.lastname: Bruins Slot
authors.forename: Wouter
authors.initials: W
authors.lastname: Koek
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Tarayre
authors.forename: Francis C
authors.initials: FC
authors.lastname: Colpaert
mesh_terms: D000465:Algorithms; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D006930:Hyperalgesia / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D010146:Pain / Q000503:physiopathology / Q000517:prevention & control; D017288:Pain Threshold / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D000700:Analgesics; D010880:Piperidines; D011725:Pyridines; C473959:befiradol