The site of action of a beta 2-receptor stimulating drug (Fenoterol) on antigen-induced bronchoconstriction

The role of vagus nerve on histamine- and acetylcholine-induced bronchoconstriction (experiments on cats)

During administration of highly concentrated acetyclcholine and histamine aerosol (20-40 min), different effects on tidal volume, respiratory rate, and bronchial tone could be demonstrated. Inhalation after vagotomy neither showed changes in respiratory rate nor in tidal volume. These results point out the importance of the nervus vagus in case of bronchoconstriction caused by mediators. It is discussed to which degree vagus activity is required for the direct effect of different mediators in living animals.

The correlation between allergen, acetylcholine and histamine-induced bronchoconstriction

A significant correlation between the degree of bronchial reactivity to ACH, Hi and A.E. was found in a series of 23 dogs. An increase in receptors sensitivity responsible for the organic manifestation of allergy must be assumed. This increased receptors sensitivity is an important phenomenon in asthma clinically relevant.

Local release of histamine, prostaglandin F2 alpha and thromboxane B2 into the tracheal lumen and its influence on airways reactivity

The influence of tracheal lavage with ascaris extract (AE) on airway response to acetylcholine (ACH) and histamine (Hi) was investigated in a series of 24 dogs. AE administered to a restricted area of the trachea resulted in a release of various mediators such as Hi, prostaglandin F2 alpha (PGF2 alpha, measured as the metabolite 15-keto-13, 14-dihydro-PGF2 alpha) and thromboxane B2 (TXB2) into the tracheal lumen. This differed from H2O administration which resulted in no increased release of these mediators. The relatively small concentrations of these substances measured in arterial plasma argue for the role of these mediators on a local basis. On the other hand, tracheal lavage with allergen induced changes in airway response to ACH and Hi aerosols which was not observed after tracheal lavage with water. An interaction between this allergen-induced mediator release into the trachea and peripheral airways reactivity could be demonstrated.

Histamine release into tracheal lumen and bronchial reactivity. Effect of local allergen administration on histamine release and bronchial reactivity

The influence of tracheal lavage with an allergen on the airway response to bronchial challenge with histamine, acetylcholine, and ascaris extract was investigated in 36 dogs. High histamine concentrations were measured in the tracheal solution after lavage with allergen. This amine, released on the mucosal surface, was observed in only very small concentrations in the circulation. Airway response to acetylcholine inhalation was significantly increased after tracheal lavage with allergen. This hyperreactivity of the lower airways induced by tracheal lavage with an allergen suggests that a reflex mechanism is involved. After histamine inhalation a significantly larger antigen-induced histamine release to tracheal lumen was observed. No influence on airway response was found after tracheal lavage with H2O.

The action of disodium cromoglycate on allergen-induced bronchoconstriction

The influence of DSCG administered to the upper and lower area of the air-conducting system on antigen-induced bronchoconstriction was studied in 34 dogs. In high doses DSCG administered to the upper airtract blocked bronchoconstriction and histamine release induced from the lower airways. Bronchoconstriction and histamine release originating from the upper airtract were not completely blocked by this kind of drug administration. Effects were differently strong in the individual animals. High doses of DSCG, administered to the lower airways, showed significant effect on bronchoconstriction originating from the lower airways. There was some yet nonsignificant effect on histamine release. Inhibition of respiratory activity without parallel inhibition of histamine release might suggest that plasma histamine concentration does not reflect the mode of action of DSCG in antigen-induced bronchoconstriction.

[Proteolytic lung emphysema and obstructive airway disease (author's transl)]

Inhalation of papain by dogs produced morphological changes corresponding to a centrolobular emphysema. The papain inhalation also induced a purulent catarrhal bronchitis. However, the functional changes seen in chronic obstructive bronchitis were not observed. During papain inhalation an increased sensitivity of the bronchial systems develops corresponding to a tremendous increase in bronchospasm in response to Acetylcholine aerosol. The parenchymal lung tissue in dogs is more vulnerable in developing emphysema after papain exposure than is teh bronchial system in developing a chronic obstructive airway disease.

[Effects of acetylcholine- and histamine inhalations also of hypoxia on the arterial plasma-histamine concentration (experiments on dogs). III. Communication (author's transl)]

Inhalation of acetylcholine causes increased histamine concentration in the arterial plasma. This increase is smaller than that following allergen inhalation. The increase in Edyn following ACH inhalation may be related to the histamine released to only a very limited extent. Comparison of the effects of histamine inhalation and allergen inhalation on Edyn and plasma histamine concentration leads to the assumption that sensory receptors are located nearer to the surface of the mucosa than that of the mast cells. Hypoxemia is followed by a slight increase in the arterial plasma histamine concentration. The increase in Edyn corresponds to that caused by allergen inhalation although the increase in Edyn and that in the plasma histamine are much smaller.

[Arterial plasma histamine concentration for airway obstruction due to different areas of the bronchial system. IV. Communication (author's transl)]

The separate inhalation of A.E. aerosol in the upper and the peripheral parts of the airways in allergic dogs is followed by an increase of the histamine concentration in the arterial plasma. The correlation between the plasma histamine concentration and dynamic elastance and the correlation between dynamic elastance and arterial oxygen pressure is very similar following the challenge of the upper and the peripheral parts of the airways. The results argue for reflex bronchoconstriction also by challenge of the more peripheral airways. The results are in accord with the idea that the answer of Edyn depends on a product of local histamine concentration and the area in which the histamine is released. The number of sensory receptors per surface area which is suspected to be greater in the upper part of the airways may also be important.

[Histamine concentration in arterial plasma in the course of repeated antigen challenges of the bronchopulmonary system. Second communication (author's transl)]

Repeated ascaris extract (A.E.) exposure on dogs sensitized against this allergen at intervals of 90, 180, and 360 min is followed by different increases in the histamine concentration in the arterial plasma. At 90 min, a significantly smaller amount of histamine becomes measurable in the arterial plasma. Edyn increases unproportionally strong. One hundred eighty minutes after the first exposure A.E. inhalation is again followed by a clearly increased histamine concentration in the arterial plasma. Edyn still increases unproportionally strong. Three hundred sixty minutes after the first A.E. exposure another exposure revealed a stronger increase in the histamine concentration in the arterial plasma, the Edyn increase being smaller than at the first exposure. These results are of importance with regard to the sensitivity of the airways and the investigation of antiallergic and bronchospasmolytic drugs.

[Arterial plasma histamine concentration during inhalation of allergen and acetylcholine before and after vagotomy. V. Communication (author's transl)]

In allergic dogs ascaris extract (A.E.) inhalation and, to a less extent, acetylcholine inhalation cause a significant increase in the histamine concentration in the arterial plasma. A.E. and acetylcholine cause a similarly strong increase in Edyn. After bilateral vagotomy A.E. and acetylcholine inhalation entail only a minimal increase in Edyn. The increase in the arterial plasma histamine concentration is as strong as before vagotomy. The results support the assumption that both A.E. and acetylcholine act on the sensory receptors of the reflexway via a reflex mechanism. PO2a decreases as Edyn increases. However, after vagotomy PO2a still decreases significantly although Edyn changes hardly. A.E. and acetylcholine are assumed to have a direct effect on the non-vagus controlled peripheral airways. The peripheral airways are mainly responsible for changes in the arterial blood gases but show no effect on Edyn or airway resistance measurements.