Imaging Striatal Dopamine Release Using a Non-Genetically Encoded Near-Infrared Fluorescent Catecholamine Nanosensor

Abraham G. Beyene; Kristen Delevich; Jackson Travis Del Bonis-O’Donnell; David J. Piekarski; Wan Chen Lin; A. Wren Thomas; Sarah J. Yang; Polina Kosillo; Darwin Yang; Linda Wilbrecht; Markita P. Landry

For further examination of the temporal resolution of nIRCats, we compared the temporal profile of evoked transients measured with nIRCats to transients measured with fast scan cyclic voltammetry (FSCV). FSCV is a technique that has been widely used to measure temporal catecholamine dynamics both in vivo and in vitro in the striatum and other brain areas. [30] [31] [32] FSCV and nIRCat experiments were conducted on separate experimental rigs with the same solutions, temperature settings, electrodes, and stimulation parameters. Evoked transients measured with FSCV and nIRCat fluorescence emission showed comparable temporal profiles in the rising phase (latency to peak: FSCV = 0.25 ± 0.0 s vs. nIRCat = 0.40 ± 0.18 s; mean ± s. d., n=4 fields of view from 2 biological replicates, p=0.23). Meanwhile, nIRCat signals exhibited a wider diversity of decay kinetics (: FSCV = 0.51 ± 0.08 s vs. nIRCats = 2.43 ± 0.24 s; mean ± s. d. n=4 fields of view from 2 biological replicates, p=0.0002). A subset of ROIs exhibited decay time constants that overlapped with, or were faster than, those of FSCV signals (Figure 3h, 3i) . We next evaluated the ability of nIRCats to detect dopamine in the presence of dopamine receptor (DR) drugs. In in vitro solution phase experiments (without biological tissue), we found that nIRCat fluorescence intensity was not modulated by exposure to 1 µM concentration of DRD2 antagonists sulpiride, haloperidol, the DRD2 agonist quinpirole, or the DRD1 antagonist SCH-23390 (Figure 4a) . Furthermore, in vitro solution phase All rights reserved. No reuse allowed without permission.