Figure 1. Dorsal Striatal D1- and D2-MSN Population Activity Displayed Similar Relationship with Locomotion in Freely Moving Mice.

A. Schematic demonstration of a miniScope carried by a mouse for in vivo imaging purpose. B. Schematic demonstration of mounting miniScope on mouse head. GRIN lens was implanted into the GCaMP6s AAV infected dorsal striatum (Green region) and anchored on the mouse skull using dental cement; miniScope base was mounted on the mouse skull using dental cement; miniScope body was secured to miniScope base through a locking screw. C. Representative fluorescent images of medium spiny neurons labeled with GCaMP6s at two different time points (Upper panels, scale bar: 100 µm). Regions of interest (ROIs) were drawn around 9 representative neurons. Traces at lower panel represented calcium transients from ROIs with matched colors. D. Quantifications of identified active neuron number (top left panel), calcium transient frequency (top right panel), calcium transient amplitude (bottom left panel), and decay time constant (bottom right panel) for D1- (Red) and D2- (Green) MSN. Each dot on the plot represented the averaged result from one mouse, and histogram bar represented the mean value for all D1- or D2- mice, with error bars representing sem. E. D1- and D2- MSN displayed similar activity during locomotion. Top panels: rasterplots of calcium transients from 140 neurons of a representative D1-Cre mouse (Left) and from 312 neurons of a representative D2-Cre mouse (Right). Bottom panels: black traces indicated locomotion velocity of the mouse. Inset panel indicated motion initiation (MI), motion termination (MT), and maximum velocity of locomotion (V_max). Horizontal scale bar: 50 seconds. F. D1- (Red) and D2- (Green) MSN displayed similar population activity during MI, MT, and V_max. Left panels indicated population activity of D1- and D2- MSN, red trace representing averaged population activity from 9 D1-Cre mice; green trace representing averaged population activity from 10 D2-Cre mice; shadowed area on the traces representing sem; black trace in each plot represented mouse locomotion velocity; vertical dotted lines indicated the exact moment for the onset of MI, MT and V_max. Right histogram plots quantified MSN population activity two seconds before and after MI, MT, and V_max. Each dot on the plot represented the averaged result from one mouse, connected with gray lines for the “pre” and “post” values of each mouse. Histogram bar represented the mean value for all D1- or D2- mice, with error bars representing sem. G. Representative mouse locomotion traces in an open field before and after cocaine injection, indicating that cocaine substantially enhanced mouse locomotor activity. H. Cocaine altered relationships between mouse locomotion velocity and D1- (Red) and D2- (Green) MSN population activity. Open circles and dashed lines indicated before cocaine injections, solid circles and solid lines indicated after cocaine injections. I. Quantification of D1- and D2- MSN population activity changes during ambulation before and after saline and cocaine injections. Each dot on the plot represented the averaged result from one mouse, and histogram bar represented the mean value for all D1- or D2- mice, with error bars representing sem. Asterisk (*) represents statistical significance.