The effect of D1-like receptor blockade on motor functions and spatial learning in B6CBA mice

Dopaminergic neurotransmitter system plays a role in many neural functions, for instance in the motor system. Dopamine also influences cognitive functions, motivation and behaviour. In this study, the effect of D1-like receptors blocker SCH 23390 on spontaneous motor activity, motor functions and spatial learning in adult wild type mice derived from the strain B6CBA was investigated. The animals of one group were administered with D1-like receptors blocker SCH 23390 while the mice from the other group were treated with the saline solution 20 minutes before experiments. Spontaneous motor activity was examined in the open field. Motor functions were examined using horizontal wire, ladder and rotarod. Spatial learning was tested in the Morris water maze. D1-like receptors inhibition significantly decreased spontaneous motor activity. In the horizontal wire test, the mice treated with SCH 23390 manifested significantly better results than control animals. No significant differences between experimental animals and controls were found in the ladder test. On the rotarod, the animals with D1-like receptors inhibition reached significantly shorter latencies than the animals treated with the saline solution. D1-like receptors blockade led to significant impairment of performance in experimental animals in the Morris water maze. Spontaneous motor activity and motor skills were influenced by evoked hypokinesia. Meanwhile in the horizontal wire test this effect seemed to be advantageous, in the rotarod test it meant a definite handicap because this test requires good motor coordination and activity. The results gained in the Morris water maze indicated that not only hypokinesia played some role there but also spatial learning and perhaps motivation were affected. The study confirmed that D1-like receptors inhibition has effects on both motor and cognitive functions in mice. However the motor effects are not the main cause of the failing in the spatial learning test.