Our study supports the view that increased activity from dopaminergic neurons in the VTA that project to the NAc promotes motivated behaviors (for review see Wheeler and Carelli, 2009). Motivated behaviors for obtaining food and cocaine in our study were attenuated by suppression of an excitatory cholinergic input to the VTA. Our findings are strikingly similar to recent findings on OxoSQ's effects on food and cocaine seeking. Systemic injections of OxoSQ suppressed both food and cocaine seeking under a FR schedule in mice (Thomsen et al., 2010). OxoSQ likely affected muscarinic type 2 and 4 receptors in LDTg/PPTg brain areas in addition to other brain areas that have these and other muscarinic receptors. Authors of this study, however, attributed some of the OxoSQ effects on activation of M1 type receptors found in the nucleus accumbens. Similar attenuation of motivated behavior is also supported by recent work on cocaine priming-induced reinstatement of cocaine seeking (Schmidt et al., 2009). Microinjection of an ionotropic glutamate receptor antagonist into the LDTg/PPTg or VTA prior to cocaine priming suppressed lever pressing during cocaine seeking reinstatement
