NAAG as a Potential Neurotransmitter at the Crayfish Neuromuscular Junction

Abstract

N-acetylaspartylglutamate (NAAG) is the most abundant peptide neurotransmitter in the mammalian central nervous system. It is composed of aspartate and glutamate, two fundamental amino acids, and modulates synaptic transmission via the activation of group II metabotropic glutamate receptors (mGluR II). In the current study, we asked whether NAAG has a similar role in non-mammals, specifically invertebrates, such as the crayfish. Our work reported here suggests that NAAG does indeed modulate synaptic transmission at the neuromuscular junction of crayfish. Metabotropic glutamate receptors, and more specifically mGluR II, facilitate the modulation. Through the application of NAAG and LY341495 (a mGluR II Antagonist), membrane depolarization was modulated after high frequency stimulation, indicating a change in synaptic transmission. Application of NAAG increased EPSP amplitude in a dose-dependent manner. Application of LY341495 decreased EPSP amplitude. Through this increased understanding of NAAGs role in the neuromuscular junction, we will enhance our knowledge of the phylogeny of NAAG and the pathways necessary for plasticity in crayfish synapses.