Widespread brain distribution of the Drosophila metabotropic glutamate receptor.

Glutamate is the predominant excitatory neurotransmitter in the vertebrate brain, whereas acetylcholine has been considered to play the same role in insects. Recent studies have, however, questioned the latter view by showing a rather general distribution of glutamate transporters. Here, we describe the expression pattern of the receptor DmGlu-A (DmGluRA), the unique homolog of vertebrate metabotropic glutamate receptors. Metabotropic glutamate receptors play important roles in the regulation of glutamatergic neurotransmission. Using a specific antibody, we report DmGluRA expression in most neuropile areas in both larvae and adults, but not in the lobes of the mushroom bodies. These observations suggest a key role for glutamate in the insect brain.