Alpha-2 adrenoceptors couple with G protein alpha-i subtype which decreases adenylyl cyclase activity, thus reducing cAMP intracellular levels resulting in smooth muscle contraction. There are three alpha-2 subtypes in humans; 2A (Kobilka BK et al, 1987), 2B (Weinshank RL et al, 1990) and 2C (Hirasawa A et al, 1993).
Hirasawa, A, Takagaki, K, Murai, M, Horie, K, Tanaka, T, Tsujimoto, G, Yano, J
Regan, JW, Caron, MG, Lefkowitz, RJ, Matsui, H, Yang-Feng, TL, Kobilka, TS, Kobilka, BK, Francke, U
Lichtblau, H, Weinshank, RL, Macchi, M, Branchek, TA, Hartig, PR, Adham, N, Zgombick, JM
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