Histamine N-methyltransferase regulates histamine-induced phosphoinositidehydrolysis in guinea pig cerebellum

We report here that the dose-response curve of the histamine-stimulated pho sphoinositide hydrolysis in the guinea pig cerebellar slices was shifted to the left when the slices were pretreated with SKF 91488 (100 muM), a speci fic inhibitor of histamine N-methyltransferase (HMT). In contrast, the pret reatment of the cerebellar slices with aminoguanidine (100 muM-1 mM), an in hibitor of diamine oxidase, had no effect on histamine-induced phosphoinosi tide hydrolysis. HMT mRNA was expressed abundantly in cerebellum, especiall y in Purkinje cells. These observations suggest that HMT regulates histamin ergic neurotransmission in guinea pig cerebellum more predominantly than di amine oxidase in histamine degradation. (C) 2001 Elsevier Science Ireland L td. All rights reserved.