The influence of theophylline and phenobarbital on rat brain 5'-nucleotidase.

Xanthines and barbiturates have opposing effects on cerebral function and metabolism. Since the xanthine theophylline is known to inhibit the enzyme 5'-nucleotidase, and thus endogenic adenosine release, an in vitro experiment was conducted on the assumption that theophylline and phenobarbital may have an opposing effect on 5'-nucleotidase activity. This assumption was confirmed. The hypothesis that barbiturates in general cause an increase in endogenic adenosine release seems compatible with the known functional and metabolic effects of barbiturates. Furthermore, accepting the hypothesis that cellular hypoxic-anoxic survival may ultimately depend on salvage of adenine nucleotides, this may even explain the dichotomy in the effect of barbiturates when used for protection of a hypoxic-anoxic insult.