The role of the vagus nerves in the respiratory and circulatory reactions to anaphylaxis in rabbits

Abstract

SUMMARY1. Rabbits, previously sensitized to egg albumen, were anaesthetized and then rendered anaphylactic by a further injection of egg albumen; total lung conductance of flow, lung compliance, breathing rate, tidal volume, end-tidal C02 %, systemic arterial and right atrial blood pressures and heart rate were measured. Before induction of anaphylaxis, some rabbits were vagotomized, some had their vagi cooled to block differential conduction, and others were paralysed and artificially ventilated to minimize secondary changes in afferent activity from the lungs and in blood gas tensions.2. Lung conductance was reduced by anaphylaxis in spontaneously breathing and in artificially ventilated rabbits, and the effect was lessened by vagal cooling and greatly reduced by vagotomy; the hyperventilation of anaphylaxis took the form of an increase in tidal volume rather than in respiratory frequency during vagal cooling, and all changes in ventilation were abolished by vagotomy. These effects are therefore dependent on the integrity of vagal nervous pathways.3. Lung compliance was reduced by anaphylaxis to a similar degree in all groups of rabbits; all groups showed similar falls in end-tidal C02%. These effects are therefore not dependent on the integrity of vagal conduction.4. Anaphylaxis reduced systemic arterial blood pressure, the response being smaller when the vagi were cooled or cut.5. It is concluded that anaphylaxis has direct actions on the pulmonary vascular bed, the distal airways or the alveoli. However, the changes in breathing, blood pressure and large airway calibre are mainly dependent on vagal reflex activity. By analogy with responses to injections of histamine

Mediators of Passive Lung Anaphylaxis in the Rat

“…It has been suggested that vagal reflexes are partly responsible for anaphylactic bronchoconstriction in guinea-pigs (Mills & Widdicombe, 1970), dogs (Gold, Kessler & Yu, 1972) and rabbits (Karczewski & Widdicombe, 1969). In our experiments, vagotomy did not modify PLA in the rat.…”

The Effects of Sodium Cromoglycate on Histamine Aerosol‐induced Reflex Bronchoconstriction in the Anaesthetized Dog

“…Widdicombe and his colleagues have studied the role of vagally mediated reflexes in the response to systemically administered antigen in guinea-pigs and rabbits. Using single fibre recordings from lung irritant receptors and the analysis of lung dynamics during anaphylaxis, they demonstrated conclusively that the vagus plays an important role in the production of anaphylactic bronchoconstriction (Karczewski & Widdicombe, 1969;Mills, Sellick & Widdicombe, 1969;Mills & Widdicombe, 1970). It is likely, therefore, that a drug which reduced the sensitivity of lung irritant receptors in man would go some way to reliving an asthmatic attack.…”

The effects of histamine, acetylcholine and 5‐hydroxytryptamine on lung mechanics and irritant receptors in the dog.

“…Secondly, other pulmonary afferent receptors may have been involved in the reflex bronchoconstrictions caused by 5-HT and possibly histamine. Paintal (1955,1974) has shown that 5-HT and histamine stimulate type J receptors in the cat lung, and there is evidence to support the concept that J receptors may be involved in reflex bronchoconstriction (Karczewski & Widdicombe, 1969;Paintal, 1977). Receptors having some of the properties of the cat J receptor have also been identified in the dog airways (Coleridge, Coleridge & Luck, 1965;Coleridge & Coleridge, 1977) and these receptors were stimulated by histamine (Coleridge & Coleridge, 1977) but the effect of such a stimulation on bronchial calibre was not investigated.…”