The present invention is based on the identification of a G-protein coupled receptor (GPCR) that is expressed predominantly in the brain and placenta and nucleic acid molecules that encoded the GPCR, which is referred to herein as the hCAR protein and hCAR gene respectively (for human Constitutively Active Receptor). Based on this identification, the present invention provides: (1) isolated hCAR protein; (2) isolated nucleic acid molecules that encode an hCAR protein; (3) antibodies that selectively bind to the hCAR protein; (4) methods of isolating allelic variants of the hCAR protein and gene; (5) methods of identifying cells and tissues that express the hCAR protein/gene; (6) methods of identifying agents and cellular compounds that bind to the hCAR protein; (7) methods of identifying agents that modulate the expression of the hCAR gene; and (8) methods of modulating the activity of the hCAR protein in a cell or organism.