Discriminative and motor performance in rats after interference with dopamine neurotransmission with spiroperidol.

The disruption of instrumental conditioning after block of central dopamine neurotransmission with drugs or lesions has been explained as an inability to initiate movements rather than as a disruption of learning mechanisms per se. To further investigate this we have developed an under-water swim maze which is a test situation that partly counteracts the akinesia of the animals. The maze has been used to test the effect of dopamine receptor inhibition by spiroperidol on a brightness and a spatial discrimination task. Aquisition was blocked and the behaviour randomized after 0.05 mg/kg and higher doses. Swim speed, however, was not affected by 0.05 mg/kg. This suggests that spiroperidol affects the acquisition of this brightness discrimination task independently of its effects on motor performance. Spatial acquisition was not affected even at 5.0 mg/kg which shows that the deficit can not be generalized to all types of acquisition.