Correlations between histamine and opioid peptides on the modulation of inflammatory processes in rats exposed to stress.

The role of mast cell histamine in body reactivity of rats under experimental stressful conditions was studied. Animals submitted to chronic anaphylactoid reactions (by injecting compound 48/80 at the dose of 1 mg/kg, i.p., twice daily, for five days), when exposed to cold-restraint stress, exhibited a fully evident inflammatory response in the carrageenin-oedema test, whereas saline-treated rats, under the same experimental conditions, showed reduced paw oedema. Interestingly, a single injection of compound 48/80 increased the pituitary content of Beta-endorphin(ir), but chronic administration failed to produce this effect suggesting that some adaptation of the organism to repeated anaphylactoid reactions may occur. These results support the hypothesis of correlations between pituitary Beta-endorphin and mast cell histamine in the reactivity of the organism to stressful stimuli.