Neurotransmitters act on cell-surface receptors to produce a wide range of effects on target cells (1 ). These effects include modulation of ion channels and changes in cellular electrical properties. Deciphering the intracellular molecular pathways by which receptor activation is transduced into alterations in cell function is often difficult owing to the accessibility to the cells to be studied in situ and the lack of regulation over both the extracellular and intracellular environment. The use of viable in vitro isolated cell models and patch-clamp recording methodology (2 ) to assay ion channel activity allows the identification of receptors and coupled intracellular signaling molecules, which regulate the response of interest. We have used whole-cell, patch-clamp recording techniques to study adrenergic receptor (AR) modulation of ion channels in ciliary epithelial cells (3 ). This approach has allowed us to measure current flowing via identified ion channels, and to identify the G-protein-coupled signaling pathway(s), which transduces AR activation to ion channel modulation.