TITLE:
Morphine has latent deleterious effects on the ventilatory responses to a hypoxic challenge*
AUTHORS:
Walter J. May, Ryan B. Gruber, Joseph F. Discala, Veljko Puskovic, Fraser Henderson Jr., Lisa A. Palmer, Stephen J. Lewis
KEYWORDS:
Morphine; Hypoxia; Minute Ventilation; Arterial Blood Gas Chemistry; Conscious Rats
JOURNAL NAME:
Open Journal of Molecular and Integrative Physiology,
Vol.3 No.4,
November
14,
2013
ABSTRACT: 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.