RESUMO
The involvement of opioid peptides in the mechanism of action of vouacapan, a new experimental compound extracted from seeds of Pterodon poligalaeflorus Benth, was investigated both in mice utilizing acetic acid writhing response and in rats utilizing inflammatory hyperalgesia induced by carrageenan and modified Randall-Selitto method. Vouacapan, in both models, caused a dose-dependent analgesia when injected p.o., s.c. and i.p. The analgesic effect was partially blocked by naloxone, nalorphine and n-methyl-nalorphine. Significant tolerance to analgesic effect was observed following repeated administration of vouacapan or morphine. On the last day of treatment, cross administration revealed symmetrical and asymmetrical cross-tolerance between vouacapan and morphine, in rats and mice, respectively. We conclude that a release of endorphins could be involved in the analgesic mechanism of vouacapan in both models tudied.
Assuntos
Analgésicos/administração & dosagem , Diterpenos/administração & dosagem , Endorfinas/fisiologia , Medição da Dor/efeitos dos fármacos , Analgésicos/antagonistas & inibidores , Animais , Diterpenos/antagonistas & inibidores , Vias de Administração de Medicamentos , Tolerância a Medicamentos , Masculino , Camundongos , Morfina/administração & dosagem , Nalorfina/análogos & derivados , Nalorfina/farmacologia , Naloxona/farmacologia , Ratos , Ratos EndogâmicosRESUMO
1. Morphine induced a contractile response in the mouse colon which consisted of two phases or components. 2. The first component was dose-related and was inhibited by tetrodotoxin, atropine and naloxone, but was insensible to hexamethonium, propranolol, phentolamine, diphenhydramine and methysergide. 3. The second component of the contractile effect was not modified by atropine, hexamethonium, propranolol, phentolamine, guanethidine or diphenhydramine, but was antagonized by naloxone, tetrodotoxin and serotonin antagonists. 4. Tachyphylaxis was observed only for the first component of the morphine induced contractile response of the mouse colon.