Effect of ozone on breathing in dogs: vagal and nonvagal mechanisms
We exposed two awake dogs with a chronic tracheostomy and the cervical vagus nerves exteriorized in skin loops to 1.0 ppm of ozone (O/sub 3/) for 2 h at intervals of 4 wk. We measured ventilatory variables before and after O/sub 3/ exposure during rest and exercise before and after vagal block. We compared the effects of vagal blockade, exercise, and O/sub 3/ on the primary determinants of breathing pattern (VT/TI, VT/TE, TI, and TE) in each of three conditions: base line (steady state), during hypercapnia, and after inhalation of 1% histamine. Under base-line conditions, O/sub 3/ increased respiratory rate and decreased tidal volume (VT) by shortening time of expiration (TE) and time of inspiration (TI) without affecting VT/TI, an indicator of the neural drive to breathing. During progressive hypercapnia, O/sub 3/ shortened TE and TI by effects both on tonic (nonvolume-related) and on phasic (volume-related) vagal inputs, and only the latter were prevented completely by cooling of the vagus nerves. Histamine-induced tachypnea was increased by O/sub 3/ and was totally blocked by cooling the vagus nerves. It was concluded that O/sub 3/ shortens the timing of respiration without increasing ventilatory drive, shortens TI and TE through vagal and nonvagal pathways, increases tonic nonvagal and phasic vagal inputs, and stimulates more than one vagal fiber type.
- Research Organization:
- Univ. of California, San Francisco
- OSTI ID:
- 6785656
- Journal Information:
- J. Appl. Physiol.; (United States), Vol. 1
- Country of Publication:
- United States
- Language:
- English
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DOGS
RESPIRATION
OZONE
TOXICITY
DYNAMIC FUNCTION STUDIES
HISTAMINE
VAGUS
AMINES
ANIMALS
AUTONOMIC NERVOUS SYSTEM
AZOLES
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
MAMMALS
NERVES
NERVOUS SYSTEM
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
VERTEBRATES
560300* - Chemicals Metabolism & Toxicology