Optogenetic excitation of ventral tegmental area (VTA) dopaminergic neurons augments place cells’ spiking.

<p>(A) Atlas schematic shows optic fiber and tetrodes in the VTA or hippocampal CA1. Images below show channelrhodopsin 2 with yellow fluorescent protein (ChR2-YFP) expression, tyrosine hydroxylase (TH) staining, and their overlay in VTA of TH::Cre rats injected with E123T/T159C virus. (B) Raster plot from 40 repetitions (above) and firing frequency (below) of optically evoked time-locked excitation of a VTA slow-spiking cell. (C) Raster plot from 40 repetitions (above) and spike count of 120 repetitions (below) of a sample place cell. Time 0 indicates the onset of the stimulation protocol. (D) Firing rate of 22 place cells 100 ms after the onset of the stimulation protocol expressed as a percentage of the prestimulation values, for control (left bar) and photostimulation (middle bar), paired <i>t</i> test: <i>t</i>(21) = −3.910, ***<i>p</i> < 0.001; the right bar shows the firing rate (% prestimulation) for 250 ms after photostimulation onset, paired <i>t</i> test: <i>t</i>(21) = −1.767, <i>p</i> = 0.092. Error bars, mean ± SEM. (E) Raster plot and spike count of a slow-spiking interneuron. (F) Spiking cross correlogram between the place cell and the interneuron shown in (C) and (E), respectively. (G) Firing rate of 21 interneurons 100 ms after photostimulation (% prestimulation), for control (left bar) and photostimulation, paired <i>t</i> test: <i>t</i>(20) = 3.002, **<i>p</i> = 0.007. The right bar shows the firing rate for 250 ms after photostimulation onset, paired <i>t</i> test: <i>t</i>(20) = 6.841, ***<i>p</i> < 0.001. Error bars, mean ± SEM. <i>Files dataset is available at Figshare public repository in Tsanov 2016 data / E123T electrophysiology and E123T immunohistology folders</i> <a href="https://figshare.com/s/b86a9a111353ba04bd32" target="_blank"><i>https</i>:<i>//figshare</i>.<i>com/s/b86a9a111353ba04bd32</i></a>.</p>