Anterior hypothalamic lesions decrease anaphylactic contractions in guinea pig trachea in vitro by reducing histamine and LTC4 reactivity

Epithelium-dependent potentiation of anaphylactic contractions by beta-endorphin in tracheae isolated from actively sensitized guinea-pigs

1. It has been shown that opioid peptides modulate airway function. In the present study, the effect of beta-endorphin on antigen-induced contractions of isolated tracheal rings from actively sensitized guinea-pigs has been studied. 2. beta-Endorphin had a concentration-dependent bimodal effect on anaphylactic contractions of the trachea. Low concentrations of beta-endorphin (10(-10) and 10(-8) M) significantly potentiated anaphylactic contractions, whereas higher concentrations (10(-7) and 10(-6) M) significantly suppressed anaphylactic contractions of guinea-pig trachea. 3. beta-Endorphin in concentrations of 10(-8) M and 10(-7) M did not affect the responsiveness of the tracheal rings to histamine or leukotriene D4. This indicates that beta-endorphin does not influence the responsiveness of tracheal smooth muscle to anaphylactic mediators. 4. In the presence of the non-selective opioid receptor antagonist naloxone, 10(-8) M beta-endorphin still potentiated the anaphylactic contractions of the trachea. In addition, an equimolar concentration of des-Tyr1-beta-endorphin, a fragment of beta-endorphin without opioid-like activity, also potentiated anaphylactic contractions. The potentiation of anaphylactic contraction by 10(-8) M beta-endorphin is not therefore mediated by classical opioid-receptors. 5. In the presence of naloxone, 10(-7) M, beta-endorphin did not suppress anaphylactic contractions of the trachea. Thus, the suppression of anaphylactic contraction is mediated via a classical opioid-receptor. 6. In epithelium-denuded trachea, both 10(-8) and 10(-7) M beta-endorphin suppressed the anaphylactic contractions, whereas 10(-8) and 10(-7) M des-Tyr1-beta-endorphin did not affect anaphylactic contractions. It is concluded that the potentiation of the anaphylactic contraction in intact trachea is epithelium-dependent whereas the suppression of the anaphylactic contraction is epithelium-independent.

Effects of anterior hypothalamic lesions and sham-operations on bacterial endotoxin-induced non-specific airway hyperreactivity in vivo and in vitro

1. In the present study the effects of anterior hypothalamic (AHA) lesions and sham-operations were investigated on the endotoxin-induced airway hyperreactivity in guinea-pigs. Unoperated, sham-operated and AHA-lesioned guinea-pigs were injected intraperitoneally with Escherichia coli endotoxin and the airway reactivity tested four days later in isolated tracheal spirals and in spontaneously breathing anaesthetized animals. Control animals were given sterile saline. 2. Sham-operated control animals demonstrated a diminished responsiveness of the tracheal spirals in vitro and of the lung resistance (delta R1) in vivo to histamine receptor and cholinoceptor-muscarinic agonists as compared to unoperated control animals. 3. AHA-lesioned control animals showed a responsiveness of the respiratory airways in vitro and in vivo between the values of unoperated and sham-operated control animals, suggesting that lesions partially restored the diminished responsiveness. 4. In unoperated and sham-operated guinea-pigs, endotoxin administration induced hyperreactivity of the tracheal spirals and delta R1 to histamine receptor and cholinoceptor-muscarinic agonists with respect to the control groups. 5. In AHA-lesioned animals, the endotoxin-induced airway hyperreactivity in vitro and in vivo to histamine receptor and cholinoceptor-muscarinic agonists was absent.

Effects of dietary poly-unsaturated fatty acids on tracheal histaminergic and cholinergic responsiveness in experimental models of bronchial hypersensitivity and hyperreactivity

Respiratory histaminergic and cholinergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between saline treated (controls) and Haemophilus influenzae treated animals in non sensitized conditions, the latter being a model for bronchial hyperreactivity, and in sensitized conditions, being a model for allergen induced bronchial hypersensitivity. The different semi-synthetic diets (35 energy% fat), varying in linoleic acid content (5.85, 11.25 and 22.05 en% fat) and one diet with low linoleic acid (3.55 en%) in which linolenic acid was added additionally (5.30 en%), exerted profound effects on tracheal reactivity to histamine. In sensitized animals the maximal induced histamine contraction was significantly diminished in the dietary group receiving 5.85 en% linoleic acid as compared with the other dietary groups (35% decrease in the H. influenzae-treated, 20-30% decrease in saline treated animals). Results in non-sensitized animals were similar, though less pronounced. No effect on food intake or growth of the animals could be demonstrated during the six week experimental periods. The carbachol induced contraction of the tracheal spirals of sensitized animals receiving low linoleic acid was also significantly decreased as compared to the other dietary groups (30% for saline treated and 20-30% for H. influenzae-treated animals). No difference in carbachol responsiveness could be detected between the different dietary groups under non-sensitized conditions. The results are discussed in view of the current concepts for bronchial hyperreactivity, especially in relation to eicosanoid involvement.