title: Desensitization to PAF-induced rat paw oedema by repeated intraplantar injections.
abstract: The intraplantar injection of PAF-acether (PAF), induced acute oedema in the rat paw, and desensitized it to subsequent challenges with the same agonist, but not to serotonin. The desensitization was maximal (up to 80% of initial response) after seven consecutive daily injections. In this condition, PAF-induced oedema of the contralateral paw was maintained. The analogue 2-methyl carbamate-PAF (2MC-PAF) was more effective than PAF as a desensitizing agent. Furthermore, the PAF-desensitized paw was refractory to challenges with 2-MC and vice-versa. PAF-acether, but not serotonin-induced rat paw oedema was inhibited by previous intravenous injection of PAF. Intravenous injections of serotonin were also effective in inhibiting selectively serotonin-induced paw oedema, but it was not possible to induce desensitization by repeated intraplantar injections of serotonin. Desensitization to PAF or the pre-treatment with the PAF antagonist BN 52021 did not block the edematogenic response induced by carrageenan.
mesh_terms: D000818:Animals; D002219:Carbamates / Q000494:pharmacology; D002351:Carrageenan / Q000494:pharmacology; D004361:Drug Tolerance; D004487:Edema / Q000139:chemically induced; D007249:Inflammation / Q000139:chemically induced*; D007267:Injections; D007275:Injections, Intravenous; D008297:Male; D010972:Platelet Activating Factor / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology
chemical_list: C050584:2-methyl carbamate-platelet activating factor; D002219:Carbamates; D010972:Platelet Activating Factor; D012701:Serotonin; D002351:Carrageenan