While they do have their limitations (e.g. developmental compensation and strain effects in mouse lines not backcrossed adequately to a parental strain for a minimum of 10 generations), use of our inbred (N20 generation) animals in the present study (where no differences in locomotor behavior were detected between D2R-/- and D2R+/+ mice; Figs. 1 &2) revealed a previously unappreciated role of D2R-mediated signaling in associative learning and attention that could not be measured with the currently available, acutely administered D2R antagonists.