Enables G protein-coupled GABA receptor activity. Involved in G protein-coupled receptor signaling pathway; negative regulation of cholinergic synaptic transmission; and response to xenobiotic stimulus. Predicted to be located in plasma membrane. Predicted to be part of G protein-coupled receptor heterodimeric complex. Expressed in nervous system. Is an ortholog of human GABBR1 (gamma-aminobutyric acid type B receptor subunit 1).