Evidencias farmacológicas de la participación del sistema opioide endógeno en la respuesta inflamatoria local de la pata de la rata

We have investigated the role of the endogenous opioíd
system (SOE) on the inflammatory response induced by
subplantar (s.p.) injection of saline (SS) and carrageenan (CA)
in the hindpaw of the rat. The administration of intraperitoneal (i.p.) naloxone was used in orden to unmask the effects
of endogenous opiates released during peripheral inflammation.
Three groups of rats received one of the following s.p.
treatments: SS, CA, orno injection (NI). Pain pressure threshold
(PPT), paw volume (edema) and local temperature were evaluated in baseline conditions and 3 h after treatment. In each
group, the effects of i.p. vehicle, naloxone and (+)-naloxone
(0.1 mg/kg) were also investigated. Both SS and Ca induced
a significan! inflammatory response with hyperalgesia, edema
and local hyperthermia. The i.p. administration of naloxone
but not that of (+)-naloxone 15 min prior to testing, significantly increased edema in ali groups of treatment (p< 0.05),
without altering PPT or local temperature. Two-away ANOVA
revealed that treatment and drugs, as well as their interaction,
had a significant impact on edema whick was related to the
effects of Ca and naloxone. Our findings illustrate the involvement of the SOE in the physiological response to local
injury, regulation microvascular leakage in the inflamed tissues.