Magnesium ions potentiate the formation of adenosine 3',5'-monophosphate induced by depolarizing agents in the rat cerebral cortex in vivo.

Pretreatment of the rat cerebral cortex by topical application of 1.5 mol X 1(-1) MgCl2 in order to prevent the induction of spreading depression by depolarizing agents did not inhibit but potentiated the ability of 1.0 mol X 1(-1) K+ (39 pmol cAMP/mg prot.) and 0.2 mol X 1(-1) veratridine [11 pmol cAMP/mg prot.] to produce the accumulation of cyclic adenosine monophosphate [cAMP] by 110% and 180% respectively. Hypertonic NaCl solutions [2.0 and 3.5 mol X 1(-1)] alone did not affect the normal cAMP levels in the cortex, neither was the effect of K+ modulated by pretreatment of the cortex by topical application of 3.5 mol X 1(-1) NaCl. Additive effects of K+ and veratridine were found on cAMP formation. The mechanism of potassium-stimulation of cAMP formation and the effect of Mg2+ is discussed.