Figure 8.

CeA ChR2 stimulation amplifies breakpoint motivation. A progressive ratio test of breakpoint was given on 2 consecutive days (counterbalanced order). On one day, rats earned laser + cocaine accompanied by its 8 s auditory cue. On the other day, rats earned cocaine alone plus its own 8 s auditory cue. On each day, effort required to obtain the next cocaine infusion increased exponentially after each earned infusion. A, CeA ChR2 rats reached higher breakpoints (maximum effort price rats were willing to pay) for laser + cocaine than for cocaine alone: making more nose pokes overall (B) and (C). Bilateral amygdala laser illumination increased motivation more than unilateral laser illumination in CeA ChR2 rats (CeA ChR2 bilateral; dark blue bars; n = 3; CeA ChR2 unilateral; light blue bars; n = 8). In contrast, control virus rats worked equally hard for cocaine regardless of laser condition and at much lower levels than CeA ChR2 rats did for laser + cocaine (CeA control virus; gray bars; n = 5). Data are shown as mean ± SEM. *p < 0.05.