Differential patterns of expression of two novel invertebrate (Lymnaea stagnalis) ionotropic glutamate receptor genes

We report the isolation of molluscan (Lymnaea stagnalis) partial complementary DNAs (cDNAs) that encode two new putative glutamate-gated cation-channel polypeptides. These proteins, which we have named Lym-eGluR4 and Lym-eGluR5, exhibit 56% identity to each other, and strong similarity (56% to 61%, and 56% to 68% identity, respectively) to the corresponding portions of vertebrate and invertebrate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-selective (or AMPA-like) glutamate receptor (GluR) subunits. Using in situ hybridisation, we have shown that the Lym-eGluR4 and Lym-eGluR5 genes are both transcribed in all 11 central ganglia of the molluscan nervous system; however, their patterns of expression are different. Interestingly, the Lym-eGluR5 mRNA is present in an identifiable neuron (RPeD1), within the right pedal ganglion, that has recently been shown to possess a GluR that can be readily activated by L-glutamate, quisqualic acid and kainic acid