Author(s)

Walter J. May¹, Ryan B. Gruber², Joseph F. Discala², Veljko Puskovic², Fraser Henderson Jr.¹, Lisa A. Palmer¹, Stephen J. Lewis^1*

¹Pediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, USA.
²Division of Biology, Galleon Pharmaceuticals, Horsham, USA.

The aim of this study was to determine whether morphine depresses the ventilatory responses elicited by a hypoxic challenge (10% O₂, 90% N₂) in conscious rats at a time when the effects of morphine on arterial blood gas (ABG) chemistry, Alveolar-arterial (A-a) gradient and minute ventilation (Vm) had completely subsided. In vehicle-treated rats, each episode of hypoxia stimulated ventilatory function and the responses generally subsided during each normoxic period. Morphine (5 mg/kg, i.v.) induced an array of depressant effects on ABG chemistry, A-a gradient and Vm (via decreases in tidal volume). Despite resolution of these morphine-induced effects, the first episode of hypoxia elicited substantially smaller increases in Vm than in vehicle-treated rats, due mainly to smaller increases in frequency of breathing. The pattern of ventilatory responses during subsequent episodes of hypoxia and normoxia changed substantially in morphine-treated rats. It is evident that morphine haslatent deleterious effects on ventilatory responses elicited by hypoxic challenge.

Morphine; Hypoxia; Minute Ventilation; Arterial Blood Gas Chemistry; Conscious Rats

J. May, W. , B. Gruber, R. , F. Discala, J. , Puskovic, V. , Henderson Jr., F. , A. Palmer, L. and J. Lewis, S. (2013) Morphine has latent deleterious effects on the ventilatory responses to a hypoxic challenge*. Open Journal of Molecular and Integrative Physiology, 3, 166-180. doi: 10.4236/ojmip.2013.34022.