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The reflex effects of alterations in lung volume on systemic vascular resistance in the dog
Author(s) -
Daly M. de Burgh,
Hazzledine Julie L.,
Ungar A.
Publication year - 1967
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1967.sp008142
Subject(s) - medicine , vascular resistance , reflex , anesthesia , vasodilation , bretylium , lung , baroreceptor , carotid sinus , hexamethonium , guanethidine , norepinephrine , blood pressure , atropine , hemodynamics , adrenergic , heart rate , stimulation , dopamine , receptor
1. The reflex effects of alterations in lung volume on systemic vascular resistance have been studied in anaesthetized dogs under conditions in which the systemic circulation was perfused at constant blood flow. The pressures in the isolated perfused carotid sinuses and aortic arch, and the arterial blood P O 2 and P CO 2 were maintained constant. 2. A maintained inflation of the lungs produced by injection of air into the trachea caused a fall in systemic arterial perfusion pressure, indicating vasodilatation. The size of the systemic vasodilator response varied directly with the pressure and volume of gas used to inflate the lungs. A similar effect was observed when the tidal volume of lungs ventilated by an intermittent positive pressure was increased. 3. Collapse of the lungs by creating a pneumothorax in closed‐chest spontaneously breathing animals evoked a systemic vasoconstrictor response which was reversed when the lungs were re‐expanded. 4. These vasodilator responses were abolished by dividing the pulmonary branches of the thoracic vagosympathetic nerves. Evidence is presented that the afferent fibres run in the cervical vagosympathetic nerves and through the stellate ganglia. 5. The responses were unaffected by atropine, but were abolished by hexamethonium, guanethidine and by bretylium tosylate, indicating that they are mediated via the sympathetic nervous system. 6. Evidence is presented that the lungs are a constant course of afferent impulses inhibiting the ‘vasomotor centre’, and that the lung inflation—systemic vasodilator reflex is a potential mechanism operating in eupnoeic breathing.