AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 3 352-G357, Copyright © 1990 by American Physiological Society
Influence of morphine or capsaicin pretreatment on rat gastric microcirculatory response to PAF
J. M. Pique, J. V. Esplugues and B. J. Whittle
Gastrointestinal Unit, Hospital Clinic, Barcelona, Spain.
Capsaicin pretreatment, which destroys primary sensory afferent neurons, or
morphine, which can inhibit peripheral sensory neurons, augments gastric
damage induced by platelet-activating factor (PAF). The concurrent effects
of such treatments on the changes in gastric mucosal blood flow (GMBF), as
estimated by hydrogen gas clearance, and in systemic arterial blood
pressure (BP) have now been determined in anesthetized rats. Intravenous
infusion of PAF (25 and 50 ng.kg-1.min-1 for 30 min) induced dose-related
histologically assessed mucosal damage, which was significantly potentiated
by neonatal capsaicin pretreatment. Capsaicin pretreatment did not affect
resting BP or GMBF or the fall in BP induced by PAF but did significantly
potentiate the PAF-induced reduction in GMBF. Likewise, morphine (1.5 mg/kg
iv) did not affect resting BP or GMBF or the fall in BP but did enhance the
reduction in GMBF and potentiated the mucosal damage after PAF infusion;
both of these effects were abolished by the opioid-antagonist naloxone (1
mg/kg iv). These findings indicate that the deleterious gastric
microcirculatory changes induced by PAF are enhanced by functional ablation
of sensory afferent neurons and by morphine, which may act on these
neurons; these effects may therefore underlie the potentiation of gastric
damage. Such local sensory neurons thus appear to be involved in the
regulation of local protective microvascular responses to noxious
challenge.
