Distribution of mRNA for histamine N-methyltransferase in the guinea pig brain

• Published in: Japanese Journal of Pharmacology Vol. 85; no. suppl.1; p. 182
• Main Authors: Junichi Kitanaka, Nobue Kitanaka, Tohru Tsujimura, Nobuyuki Terada, Motohiko Takemura
• Format: Journal Article
• Language: Japanese
• Published: The Japanese Pharmacological Society 2001
• ISSN: 0021-5198; 1347-3506

Histamine N-methyltransferase (HMT, EC 2.1.1.8) followed by monoamine oxidase B is the sole inactivating pathway of neuronal histamine, because of lack of diamine oxidase (EC 1.4.3.6), another histamine degrading enzyme, in the mammalian central nervous system. This suggests that HMT is a key enzyme in termination of histaminergic neurotransmission. The tissue distribution of HMT is reported to be different among species. In the guinea pig tissues, HMT mRNA is expressed most abundantly in both brain and small intestine, although little signal is detected in kidney and liver. Therefore, guinea pigs are useful for investigating brain distribution of HMT mRNA. To know the exact localization of HMT mRNA, we visualized HMT mRNA expression by in situ hybridization with the guinea pig HMT cDNA we have previously cloned. The strong hybridization signal was observed in Purkinje cell layer and nucleus solitary tract. In contrast, no signal was detected in the hippocampus or striatum. These observations were supported by Northern blotting analysis using total RNA samples from different brain regions： the strong signal was detected in cerebellum, thalamus + hypothalamus, and brain stem, although the hybridization signal was weak or undetectable in hippocampus and striatum. Therefore, HMT seems to have an important function in cerebellum and brain stem.