Multiplexed neurochemical monitoring reveals glutamate modulates dopamine neurotransmission in the nucleus accumbens

Dopamine (DA) and glutamate (Glu) play vital roles in cognitive function, motor control, reward systems, and addiction. However, neurotransmitters are typically measured one at a time instead of simultaneously, which would allow a better picture of neurotransmitter interactions. In this study, we multiplexed dopamine detection using fast-scan cyclic voltammetry (FSCV) and glutamate detection using genetically encoded iGluSnFR fluorescent probes to simultaneously investigate dopamine and glutamate signaling in mouse nucleus accumbens slices. We perturbed glutamate transmission to identify how faster synaptic glutamate regulated slower dopamine volume transmission. After bathing brain slices in a buffer containing 100 μM glutamate, dopamine release decreased by nearly half. We then used drugs to inhibit different glutamatergic proteins to test their effects on dopamine release. Blocking the excitatory amino acid transporter (EAAT2) using DL-TBOA (20 μM) increased glutamate concentrations and decreased dopamine release. Blocking metabotropic glutamate receptors (mGluR2/3) with LY 341495 (40 μM) did not affect dopamine release and the mGluR2 agonist LY 379268 (10 μM) also did not affect dopamine release, so the effect was not mediated by metabotropic group 2/3 receptors. Blocking NMDAR with D-AP5 (50 μM) decreased glutamate but did not change dopamine release. Blocking AMPA/kaintate receptor function with NBQX (5 μM) did not change glutamate release but did increase dopamine release. This work demonstrates the importance of simultaneous detection of related neurotransmitters while showing that glutamate and dopamine release have an inverse relationship that is partially mediated by binding to AMPA and Kainate receptors.