IMR Press / JIN / Volume 22 / Issue 6 / DOI: 10.31083/j.jin2206160
Open Access Original Research
Imaging of Evoked Cortical Depolarizations Using Either ASAP2s, or chi-VSFP, or Di-4-Anepps, or Autofluorescence Optical Signals
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1 Neuroscience, UConn Health, School of Medicine, Institute for Systems Genomics, Farmington, CT 06030, USA
2 Center for Laser Microscopy, Institute of Physiology and Biochemistry “Jean Giaja”, Faculty of Biology, University of Belgrade, 11000 Belgrade, Serbia
3 Department of Physiology, Institute of Health Sciences, Yeditepe University, 34755 Istanbul, Turkey
4 Departments of Neurobiology, Bioengineering, and Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
*Correspondence: (Srdjan D. Antic)
J. Integr. Neurosci. 2023, 22(6), 160;
Submitted: 8 July 2023 | Revised: 11 August 2023 | Accepted: 14 August 2023 | Published: 6 November 2023
Copyright: © 2023 The Author(s). Published by IMR Press.
This is an open access article under the CC BY 4.0 license.

Background: Population voltage imaging is used for studying brain physiology and brain circuits. Using a genetically encoded voltage indicator (GEVI), “VSFP” or “ASAP2s”, or a voltage-sensitive dye, Di-4-Anepps, we conducted population voltage imaging in brain slices. The resulting optical signals, optical local field potentials (LFPs), were used to evaluate the performances of the 3 voltage indicators. Methods: In brain slices prepared from VSFP-transgenic or ASAP2s-transgenic mice, we performed multi-site optical imaging of evoked cortical depolarizations - compound excitatory postsynaptic potentials (cEPSPs). Optical signal amplitudes (ΔF/F) and cEPSP decay rates (OFF rates) were compared using analysis of variance (ANOVA) followed by unpaired Student’s t test (31–104 data points per voltage indicator). Results: The ASAP2s signal amplitude (ΔF/F) was on average 3 times greater than Di-4-Anepps, and 7 times greater than VSFP. The optical cEPSP decay (OFF rate) was the slowest in Di-4-Anepps and fastest in ASAP2s. When ASAP2s expression was weak, we observed slow, label-free (autofluorescence, metabolic) optical signals mixed into the ASAP2s traces. Fast hyperpolarizations, that typically follow depolarizing cortical transients (afterhyperpolarizations), were prominent in ASAP2s but not present in the VSFP and Di-4-Anepps experiments. Conclusions: Experimental applications for ASAP2s may potentially include systems neuroscience studies that require voltage indicators with large signal amplitude (ΔF/F), fast decay times (fast response time is needed for monitoring high frequency brain oscillations), and/or detection of brain patches in transiently hyperpolarized states (afterhyperpolarization).

cerebral cortex
excitatory postsynaptic potentials
temporal summation
paired pulse facilitation
65539/Cure Alzheimer’s Fund
U01MH109091/National Institute of Mental Health
AG064554/National Institute on Aging
P50AA027055/UConn Health Alcohol Research Center (ARC)/Kasowitz Medical Research Fund
Fig. 1.
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