“…For example, we have found that pretreatment (priming) with 3 injections, spaced 3-6 days apart, of D1, D2 or D1/D2 dopamine agonists permits a behaviorally ineffective dose of the D2 agonist quinpirole (0.25 mg/kg) to produce robust contralateral rotational behavior in 6-OHDA rats, suggesting that prior exposure to a dopamine agonist greatly influences the subsequent behavioral response following challenge with a D2 agonist [17,18] . While some of the acute behavioral effects of caffeine in 6-OHDA rats have been characterized [10,11,13] , less is known about the role of caffeine in sensitizing (priming) dopamine-mediated behaviors in 6-OHDA rats. One study reported that intermittent, repeated treatment with caffeine (15 mg/kg) could sensitize D1-mediated contralateral rotational behavior, however, there was no effect on D2-mediated rotational behavior [19] ; this is a surprising observation given the wealth of data regarding D2/A2a receptor interactions [3-6, 20, 21] ( fig.…”