Naloxone Exacerbates Intestinal and Systemic Anaphylaxis in the Rat

Following sensitization to ovalbumin (OA), male Wistar rats were pretreated with naloxone (20 mg/kg i.p.) and subjected to antigen challenge (3 mg OA i.p.). Naloxone exacerbated both systemic and intestinal anaphylaxis when injected 10 and 90 min before the antigen challenge. This was evidenced by a more pronounced drop in rectal temperature, higher hematocrit values, and by an enhanced elevation of basal short-circuit current (an indication of …