The present experiments uncover a multiplicity of regulatory mechanisms that converge to control DA release elicited by the selective activation of CINs. In behaving animals, CINs encode reward-related events (Morris et al., 2004). While DA neurons increase or decrease their basal firing rate in response to the presentation or omission of reward, CINs respond with a brief pause independently of the outcome (Aosaki et al., 1994; Morris et al., 2004). This has been interpreted as the establishment of the appropriate temporal window for contingencies to be encoded, while DAergic responses are theorized to carry a learning signal about future outcomes (Morris et al., 2004). Here, we determined that in vivo DA release is in fact triggered by endogenous release of ACh. This allows new considerations to be taken into account for the way that CIN activity may set the stage for DA neuron activity to produce its postsynaptic effects. Reward-related activity of CINs consists of several phases (initial rise, pause, and second rise) (Morris et al., 2004; Aosaki et al., 1994; Shimo and Hikosaka, 2001; Apicella et al., 1991, 2011;
