Experimental acute hypoxia. Brain preservation by phenobarbital pretreatment. Histological study in guinea pigs

Acute hypoxia was induced by keeping guinea pigs in an atmosphere of 5% O2/95% N2 for 20 min. Four groups of 10 guinea pigs each were used: (A) control; (B) after 20 min of hypoxia; (C) after 20 min of hypoxia and 20 min of oxygen therapy (100%); (D) pretreatment with phenobarbital (100 mg/kg body wt) and 20 min of hypoxia, followed by 20 min of oxygen therapy. The histological study did not show significant differences between barbiturate-treated and untreated hypoxic brains. In fact, the severity of ischemic-hypoxic damage as well as its distribution were similar in all the experimental groups of animals. Lesions predominated in the regions which are known to be more sensitive to hypoxia (3rd and 4th layers of parieto-occipital cortex, Sommer's fields, cerebellum). It is considered that in the experimental conditions barbiturates did not act as a protective agent--at least as assessed morphologically.