We present a new approach for imaging intracellular neurotransmitter molecules with stimulated Raman scattering microscopy. We leverage the isolated vibrational peaks of carbon-deuterium bonds to observe these neurotransmitters directly and quantitatively. By using deuterated versions of neurotransmitters, we minimize perturbation to neurochemical activity with respect to previously demonstrated fluorescence-based methods. We show direct imaging of deuterated dopamine and GABA uptake and release dynamics in PC12 chromafin cells, and in primary hippocampal neurons, respectively. Specifically, we show that stimulation of neurotransmitter release results in a 20-50% intracellular neurotransmitter concentration reduction, with the ability to observe inter- and intracellular variation in vesicular neurotransmitter release. Taken together, our data suggest that neurotransmitter isotopologues can serve as a generic, commercially-available, non-perturbative, and biocompatible method to image neurotransmitters that are chemically homologous to their native counterparts.
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