The barrier choice paradigm: haloperidol reduces sensitivity to reinforcement.

The standard choice situation was modified by placing a 76 cm high barrier between two levers. To travel between levers, rats had to climb the barrier. Four doses of haloperidol were assessed for effects on motor and motivational systems. The drug impeded the rats' ability to climb the barrier. Residence and travel times increased, and changeover rates decreased. Pressing the levers was not entirely suppressed by haloperidol. The slope of the matching law decreased with increasing doses of haloperidol, showing reductions in the rats' sensitivity to reinforcement. The notion that neuroleptics impair the initiation or execution of complex motor acts and disrupt food-locomotion activity, is supported by these results.