Effect of quinpirole on timing behaviour in the free-operant psychophysical procedure: evidence for the involvement of D2 dopamine receptors

Abstract
Operant timing behaviour is sensitive to dopaminergic manipulations. It has been proposed that this effect is mediated principally by D2-like dopamine receptors. However, we recently found that the effect of d-amphetamine on timing in the free-operant psychophysical procedure was mediated by D1-like dopamine receptors. It has not been established whether stimulation of D2-like receptors affects timing in this schedule.