Fig. 2

Chronic morphine effects on VTA DA soma size differ based on projection target. a. TH-Cre mice received bilateral infusions of retrograde AAV5-DIO-FP into the NAc or PFC and VTA DA neuron soma size was measured following chronic morphine or sham pellet administration. b. Timeline of experimental paradigm. Morphine or sham pellets were implanted on days 1 and 3 (d1, d3) and tissue was collected on day 5. c. Male and female mice showed similar free morphine concentration in blood serum (student t-test, n.s., p > 0.05) d. Heatmaps of combined images used in morphine studies showing distinction in NAc medial shell (m.shell)- and core-projecting VTA DA neurons. Representative images were taken using 10X objective, scale bar = 100 μm. Top images: NAc infusion sites, Bottom images: labeled VTA DA neurons. e. Morphine decreases the soma size of NAc m.shell-projecting VTA DA PN neurons with no effect on VTA DA PN neurons that project to the NAc core. Number of mice in each group is noted within columns and 7–26 neurons were analyzed per mouse. *denotes significant effect of morphine on soma size (two-way ANOVA, Tukey’s post-hoc test, p < 0.05). f. Heatmap of PFC infusion sites used in morphine studies. Representative images were taken using 10X objective, scale bar = 100 μm. g. Soma size of VTA DA neurons that project to the PFC is increased following chronic morphine treatment. Number of mice in each group is noted within columns and 4–12 neurons were analyzed per mouse (student t-test, *p < 0.05)