Enables group III metabotropic glutamate receptor activity. Predicted to be involved in several processes, including adenylate cyclase-inhibiting G protein-coupled glutamate receptor signaling pathway; detection of mechanical stimulus involved in sensory perception of pain; and modulation of chemical synaptic transmission. Predicted to act upstream of or within signal transduction. Predicted to be located in neuron projection; neuronal cell body; and presynaptic membrane. Predicted to be integral component of plasma membrane. Is expressed in several structures, including eye; gonad; ileum; liver and biliary system; and nervous system. Human ortholog(s) of this gene implicated in attention deficit hyperactivity disorder; autistic disorder; and schizophrenia. Orthologous to human GRM8 (glutamate metabotropic receptor 8). [provided by Alliance of Genome Resources, Apr 2022]