Ana Baamonde1, 2, *, Marco 輙varez-Vega1, Agust地
Hidalgo2 and Luis Men始dez2
1Laboratorioﾊde Farmacolog誕, Departamento de Medicina, Facultad
de Medicina, Universidad de Oviedo,
Juli㌻ Claver誕 s/n, 33006 Oviedo, Asturias, Spain
2InstitutoﾊUniversitario de Oncolog誕 del Principado de Asturias,
Asturias, Spain
*ﾊTo whom correspondence should be addressed(1).
Abstract: We studied the effects of intraplantar morphine in
the formalin test in mice. Intraplantarly administered morphine (30-300ﾊmg)
induced analgesic effects at lower doses than intraperitoneally administered
morphine. Following the administration of [3H]morphine, the %
of radioactivity present in brain was the same by either route. In contrast,
higher radioactivity values appeared in the injected paw in those mice intraplantarly
injected. Since local morphine induces analgesia at doses lower than the
intraperitoneally administered drug, especially in the second phase of the
test, and the access to brain is undistinguishable, we propose that local
morphine enhances central opiate analgesia in the formalin test in mice.
Keywords: Peripheral analgesia, Intraplantar morphine, Formalin test