Figure 6. RXRα overexpression in NAc increases motivation to self-administer low cocaine doses.

(A) Experimental design for behavioral economics testing, using male rats (n = 8/group).

(B) Total cocaine intake in FR1 sessions was significantly reduced by RXRα overexpression (unpaired Welch’s t-test: t_8.5723 = 2.3018, p = 0.04824).

(C) Dose response curves in the threshold procedure showed increased responding for low doses of cocaine after RXRα overexpression (LMM-ANOVA: interaction Dose:Virus: FF_9,126 = 5.4513, p = 0.00000261, followed by Sidak’s post hoc tests).

(D) Averaged demand curves showed a similar trend of increased cocaine intake at higher prices (LMM-ANOVA: interaction Price:Virus: F_9,126 = 1.2085, p = 0.2955).

(E) Representative example of task performance in the threshold procedure (from an HSV-GFP control), highlighting mathematical demand curve fitting and extraction of behavioral economics parameters.

(F) Consumption at low effort Q₀ (unpaired Welch’s t-test: t_13.987 = 1.9359, p = 0.07336) and

(G) consumption at maximum effort Q_max (unpaired Welch’s t-test: t_13.977 = 1.899, p = 0.0784) both trended toward a decrease after RXRα overexpression.

(H) Motivation metrics P_max (unpaired Welch’s t-test: t_8.0394 = −2.3802, p = 0.04439) and

(I) O_max (unpaired Welch’s t-test: t_8.6305 = −3.2097, p = 0.01126) were both increased by RXRα overexpression.

(J) Demand elasticity α was reduced by RXRα overexpression (unpaired Welch’s t-test: t_12.208 = 2.4121, p = 0.0325).

Bar graphs and line graphs represent mean ± SEM.