The effect of the adenosine A(2A) antagonist KW-6002 on motor and motivational processes in the rat.

ABSTRACT

RATIONALE It is well established that humans and rats respond to an imperative stimulus more rapidly as a function of the foreperiod preceding the target, and with this decrease in mean response time, there is also an increase in anticipatory (prior to the signal) responses. These changes reflect enhanced motor readiness. Also, reaction times are quicker when the cost of reward (amount of work required) is minimum. Antagonism of the adenosine A(2A) receptor has been shown to effect motor-related processes. OBJECTIVE: This study examined the behavioural effects of systemic administration of the adenosine A(2A) antagonist KW-6002 in a cued reaction time task in the rat. The purpose of this study is to ascertain whether KW-6002 would enhance motor readiness and effect performance as a function of reward cost. METHODS: Rats were trained on a visually cued reaction time task with variable foreperiods, and the effects of three doses of KW-6002 (0.3, 1.0 and 3.0 mg/kg systemically, compared to vehicle) were examined. RESULTS: Increasing doses of KW-6002 resulted in faster reaction times and an increase in the number of anticipatory responses. KW-6002 enhanced the foreperiod effect on reaction time distributions and anticipatory responses. In addition, KW-6002 had differential effects on performance between rewarded and unrewarded trials. CONCLUSION: Antagonism of adenosine A(2A) receptors by systemic KW-6002 speeds reaction time and enhanced motor preparatory processes as well as interacting with motivational processes.