ALTERATIONS OF THE ADENYLYL-CYCLASE SYSTEM IN MECOBALAMIN-DEFICIENT RATS

Vitamin B-12 deficiency is sometimes found in patients with psychiatri c disorders. The mechanism by which vitamin B-12 affects neuronal cell function in vivo, however, remains elusive. In this communication, we investigated how vitamin B-12 affected the adenylyl cyclase (AC) sign al transduction system in vitamin B-12 (mecobalamin)-deficient rat cer ebral cortex. Rats were fed with or without mecobalamin for 15 weeks. Basal, GppNHp-, forskolin- and MnCl2-stimulated AC activities were sig nificantly lower in mecobalamin-deficient rats than in controls. [H-3] Forskolin binding and autoradiography of brain slices showed that bind ing of forskolin in the mecobalamin-deficient rat brain was decreased compared with that in controls. The present study may indicate that vi tamin B-12 participates in the regulation of the function of AC cataly tic subunits and/or coupling between the stimulatory GTP-binding prote in, Gs, and the catalytic subunits of AC.