In addition to these behavioral measures of impulsivity, SHRs exhibited increased hyperactivity during ITD (F1,29=49.22, p<0.001, Supplementary Fig. 2d) and increased novelty seeking when placed in a novel open-field arena (F1,14=22.10, p<0.001, Fig. 1c). Moreover, SHRs were more sensitive to heroin’s acute neurochemical and behavioral effect. While there was no baseline difference in extracellular dopamine levels in the AcbC between the two strains (t8=1.10, p=0.30), SHRs exhibited a more pronounced heroin-induced increase (F9,72=3.39, p=0.002, Fig. 1d, upper panel), consistent with their enhanced locomotor response (F8,96=6.18, p<0.001, Fig. 1d, lower panel).
