gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via ionotropic (GABA(A) and GABA(C)) and metabotropic (GABA(B)) receptors. The GABA(B) receptor is a dimer composed of R1 and R2 components. In addition to their location on neurons, GABA and functional GABA(B) receptors also have been detected in some peripheral tissues. In the present study, we combined immunohistochemistry, immunoblot and tension recording to determine if the human fallopian tube express glutamic acid decarboxylase (GAD65/67), two isoforms for synthesis of GABA and functional GABA(B) receptors. Immunoblots showed that the human fallopian tube tissue contained GABA(B)R1 protein which was localized in the epithelial cells and smooth muscle cells by immunohistochemistry. In addition, epithelial cells also expressed GAD65/67. Tension recording found that both GABA and baclofen, a GABA(B) receptor agonist increased the spontaneous activity of human fallopian tube. The expressions of GABA(B)R and GAD65/67 were significantly upregulated in the ectopic pregnancy group than in the intrauterine pregnancy group. We conclude that the human fallopian tube is capable of synthesizing GABA and expresses functionally active GABAB receptors. An upregulation of GABA synthesis and corresponding GABA(B) receptors may involve in ectopic pregnancy. (C) 2010 Elsevier Inc. All rights reserved.