Effect of naloxone on regional cerebral blood flow during endotoxin shock in conscious rats

Maintenance of cerebral blood flow (CBF) is vital during cardiovascular shock. Since opioids have been implicated in the pathophysiology of endotoxin shock and have been shown to alter cerebral perfusion patterns, we determined whether opioids were responsible for any of the changes in regional CBF observed during endotoxin shock and whether the use of naloxone might impair or aid in the maintenance of CBF. When blood flow (BF) is studied with microspheres in rats, the left ventricle of the heart is often cannulated via the right carotid artery. Questions have arisen concerning the potential adverse effects of this method on CBF in the hemisphere ipsilateral to the ligated artery. We measured right and left regional CBF by use of this route of cannulation. Twenty-four hours after cannulations were performed, flow measurements were made using radiolabeled microspheres in conscious unrestrained male Sprague-Dawley rats (300-400 g) before and 10, 30 and 60 min after challenging with 10 mg/kg Escherichia coli endotoxin (etx) or saline. Naloxone (2 mg/kg) or saline was given as a treatment 25 min post-etx. We found no significant differences between right and left cortical, midbrain, or cerebellar BF at any time in any treatment group. After etx, the whole brain received a large share of the depressed cardiac output. Thus global CBF was not significantly reduced below its pre-etx value, an effect unaltered by naloxone. Regionally, BF was reduced to cerebellum and midbrain by 30 min post-etx. Naloxone prevented this depression. No region was affected to a greater or lesser degree than others.(ABSTRACT TRUNCATED AT 250 WORDS)