Histamine-induced cyclic AMP accumulation in type-1 and type-2 astrocytes in primary culture

Abstract

Histamine-induced cyclic AMP (cAMP) accumulation was studied in purified primary cultures of type-1 and type-2 astrocytes from neonatal rat brain. Histamine induced remarkable cAMP accumulation in type-1 astrocytes in a dose-dependent manner (EC 50 = 1.2 × 10 −5 M, E max = 1100% of control). In contrast, histamine had no significant effect on cAMP accumulation in type-2 astrocytes. Famotidine, an H 2-antagonist, dose-dependently inhibited histamine-induced cAMP accumulation in type-1 astrocytes (K i = 3 × 10 −8 M), but mepyramine (10 −6 M), an H 1-antagonist, had no effect. Dimaprit and impromidine, H 2-agonists, stimulated cAMP accumulation, but 2-pyridylethylamine, an H 1-agonist, did not stimulate it nor augment the H 2-agonist-induced cAMP accumulation. These results indicate that (1) histamine induces cAMP accumulation in type-1 astrocytes but not in type-2 astrocytes, and that (2) histamine-induced cAMP accumulation in type-1 astrocytes is mediated by H 2-receptors without significant augmentation via H 1-receptors.