Operant self-stimulation of nigral dopamine neurons.

<p>The number of active (A) and inactive (B) lever presses during the first 10 testing sessions: ChR2-expressing mice rapidly acquire lever pressing for dopamine stimulation, whereas YFP control mice do not. (C) Following reversal of the active and inactive levers, mice (<i>n = </i>3) changed their preference. (D) There was no effect of “satiety.” Self-stimulation behavior did not decrease when the animals received a second session immediately after the first. (E) Mice press the active lever less frequently for 1-Hz stimulation than they do for 50-Hz and 10-Hz stimulation (<i>* p</i><0.05). (F) The number of inactive presses is not affected by stimulation frequency. Values are mean ± s.e.m.