title: Tonic beta-sympathetic activity in the lung periphery in anesthetized dogs.
abstract: The present study was undertaken to determine whether beta-adrenoceptors could be physiologically detected in the lung periphery and whether they were under tonic stimulation in the resting state in anesthetized dogs. A fiberoptic bronchoscope was wedged in a sublobar segment of lung in anesthetized male mongrel dogs for measurement of resistance through the collateral system (Rcs). beta-Agents were delivered locally as aerosols through the bronchoscope, and the response was evaluated by changes in Rcs. Distilled water alone produced a mean increase of 8.5 +/- 2.43% (SE) in Rcs at 2 min in six dogs, whereas dl-isoproterenol produced a mean decrease of 8.9 +/- 2.10% (P less than 0.03), thus demonstrating the presence of submaximally stimulated beta-receptors. To test whether the beta-receptors were under tonic stimulation, we compared the effect of aerosolized d- and dl-propranolol in 5 dogs. d-Propranolol that lacks significant beta-blocking activity and dl-propranolol both produced large transient increases in Rcs. However, with d-propranolol, Rcs had returned to base line at 15 min, whereas with dl-propranolol Rcs remained elevated at a mean of 20% above base line for greater than 2 h (P less than 0.01). Local timolol aerosol also produced a sustained increase in Rcs. After pretreatment with reserpine or after bilateral adrenalectomy, both d- and dl-propranolol still produced large transient increases in Rcs, but dl-propranolol no longer produced a sustained increase. Neither isoproterenol nor atropine affected Rcs in the presence of dl-propranolol, nor did pretreatment with atropine affect the response of Rcs to dl-propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000315:Adrenalectomy; D000336:Aerosols; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004285:Dogs; D007545:Isoproterenol / Q000494:pharmacology*; D008168:Lung / Q000294:innervation*; D008297:Male; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013237:Stereoisomerism; D013564:Sympathetic Nervous System / Q000502:physiology*; D013999:Timolol / Q000494:pharmacology
chemical_list: D000336:Aerosols; D011943:Receptors, Adrenergic, beta; D001285:Atropine; D013999:Timolol; D011433:Propranolol; D007545:Isoproterenol