Enables G protein-coupled neurotransmitter receptor activity involved in regulation of postsynaptic membrane potential. Acts upstream of or within gamma-aminobutyric acid signaling pathway. Located in several cellular components, including GABA-ergic synapse; Schaffer collateral - CA1 synapse; and synaptic membrane. Part of G protein-coupled receptor dimeric complex. Is expressed in several structures, including central nervous system; eye; genitourinary system; gut; and respiratory system. Orthologous to human GABBR1 (gamma-aminobutyric acid type B receptor subunit 1). [provided by Alliance of Genome Resources, Apr 2022]