Project description Fast -scan cyclic voltammetry was coupled with carbon microelectrodes for co-detection of dopamine and met-enkephalin at single recording sites in rat striatal slices. The measurements used a specifically designed voltammetric waveform to minimize sensitivity to dopamine, maximize sensitivity to enkephalin, and to minimize biofouling. Both neurotransmitter (dopamine) and neuropeptide (enkephalin) release scaled with stimulation duration. Enkephalin dynamics displayed a unique biphasic profile with a significant latency to peak that occurred ~30 seconds after stimulation. The data suggests a sphere of influence that is ~3x larger than that of dopamine and that is consistent with multiple forms of the peptide released at once. Signals were validated by mass spectrometry of collected striatal relesates. The findings provide direct evidence to support widely held assumptions regarding neuropeptide release, and they demonstrate how these signaling molecules can affect distinct cellular populations in striatum, even when recorded at the same site.