Abstract: | Excised middle cerebral and basilar arteries from dogs were incubated in Krebs-Ringer bicarbonate solution and exposed to normal, high and low concentrations of magnesium [Mg] in the medium. Sudden withdrawal of extracellular Mg2+ ([Mg2+]o) from the medium produced contraction of arterial smooth muscle, whereas elevated concentrations of [Mg2+]o decreased the basal tensions in a concentration-dependent manner. |