PENTOBARBITAL ENHANCES CYCLIC ADENOSINE-MONOPHOSPHATE PRODUCTION IN THE BRAIN BY EFFECTS ON NEURONS BUT NOT GLIA

Background: Cyclic adenosine monophosphate (cAMP) is an important regu lator of neuronal excitability. The effects of barbiturates on cAMP pr oduction in intact neurons are not known, This study used cultures of cortical neurons, cultures of glia, and slices of cerebral cortex from the rat to study the effects of barbiturates on cAMP regulation in th e brain. Methods: Primary cultures of cortical neurons or glia were pr epared from 17-day gestational Sprague-Dawley rat fetuses and were use d after 12-16 days in culture. Cross-cut slices (300 mu m) were prepar ed from cerebral cortex of adult rats. Cyclic AMP accumulation was det ermined by measuring the conversion of [H-3]adenosine triphosphate (AT P) to [H-3]cAMP in cells preloaded with [H-3]adenine. Results: Pentoba rbital enhanced isoproterenol- and forskolin-stimulated, but not basal , cAMP accumulation in cultures of cerebral neurons, Cyclic AMP produc tion was enhanced by pentobarbital in a dose-dependent fashion up to a concentration of 250 mu M; This concentration of pentobarbital increa sed cAMP production by 40-50% relative to that in controls without pen tobarbital, At 500 mu M pentobarbital, the magnitude of the enhancemen t was less. Pentobarbital had no effect on isoproterenol-stimulated cA MP production in cultures containing only glia. Pentobarbital also enh anced isoproterenol-stimulated, but not basal, cAMP production in slic es of cerebral cortex by similar to 30% at concentrations of 62.5-250 mu M and by almost 100% at 500 mu M. Conclusions: Pentobarbital enhanc es stimulated cAMP accumulation in cultured preparations from brain an d fresh cortical slices. Neurons are required for this effect, Because cAMP modulates neuronal excitability, this effect of pentobarbital ma y be an important mechanism by which this anesthetic influences brain function.