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Cyclic nucleotide metabolism in experimental bronchial constriction in rabbits
Respiration; International Review of Thoracic Diseases
|January 1, 1978
Summary
Bronchoconstriction in rabbits was induced by saline, acetylcholine, and histamine. Parasympathetic nerve stimulation, not direct smooth muscle contraction, mediated saline and acetylcholine effects via cGMP/cAMP ratio changes.
Area of Science:
- Pulmonary Physiology
- Respiratory Medicine
- Pharmacology
Background:
- Airway resistance is modulated by various stimuli.
- The role of the parasympathetic nervous system in bronchoconstriction is complex.
- Cyclic nucleotide signaling pathways (cGMP/cAMP) are implicated in smooth muscle function.
Purpose of the Study:
- To investigate the mechanisms of bronchoconstriction induced by different agents in rabbits.
- To determine the involvement of the parasympathetic nervous system in these responses.
- To explore the relationship between bronchoconstriction and intracellular cyclic nucleotide levels.
Main Methods:
- Intratracheal administration of isotonic saline, acetylcholine (Ach), and histamine (His) in anesthetized rabbits.
- Measurement of airway resistance and arterial oxygen partial pressure (pO2).
- Bilateral cervical vagotomy to assess parasympathetic nerve involvement.
- Analysis of the cyclic guanosine monophosphate (cGMP) to cyclic adenosine monophosphate (cAMP) ratio.
Main Results:
- Saline, Ach, and His significantly increased airway resistance and decreased pO2.
- Vagotomy largely inhibited saline- and Ach-induced bronchoconstriction but only partially affected His.
- Bronchoconstriction from saline and Ach correlated with increased cGMP/cAMP ratio; His did not show a similar correlation.
Conclusions:
- Bronchoconstriction can be mediated by parasympathetic nerve stimulation or direct smooth muscle contraction.
- Parasympathetic nerves do not appear to regulate alveolar ventilation.
- Parasympathetic-induced bronchoconstriction is linked to an elevated cGMP/cAMP ratio.