Norepinephrine increases cyclic GMP in astrocytes by a mechanism dependent on nitric oxide synthesis

Norepinephrine induces a rapid and concentration-dependent rise (EC₅₀ = 1.21 ± 0.33 μM) in cyclic GMP levels in astrocyte-enriched cultures from rat brain. The response is partially mediated by α₁-adrenoceptors since a marked inhibitory observed in the presence of prarosin while the ß-antagonist propranolol shows a smaller effect and the α₂-antagonist yohimbine is ineffective l-N^G-methylarginine, an inhibitor of nitric oxide synthesis from l-arginine, blocks the norepinephrine-induced cyclic GMP accumulation. This effect is reversed by l-arginine.