Effects of haloperidol on a run-climb-run behavioral task: distance climbed does not alter within-session decrements

Effects of haloperidol (0.04-0.32 mg/kg) were assessed in 10 hungry rats trained in a 10-trials-per-day format to run down an alleyway, climb a vertical rope, and run across a horizontal board to obtain sweetened milk. Rope lengths of 0.59 m and 1.32 m defined low- and high-effort requirements, respectively. Haloperidol produced substantial within-session decrements on Trials 2-10, but the drug did not affect rope-climbing speed more than horizontal running speed. Drug-induced within-session decrements were similar for both low- and high-effort requirements. After treatment with the 0.16-mg/kg dose, force-time waveforms of the climbing behavior documented instances of arrest of movement on the rope, but no bradykinesia of individual locomotor acts was discerned. Results suggest that haloperidol may produce associative deficits as well as disruptions of motor processes.