Influences of Dopamine D2, D3 Agonist Quinpirole Dosage on Locomotor Activity Measured by Open-Field Test

Background: Dopamine D2 and D3 receptor agonist quinpirole have been tried as one of drug-induced bipolar animal models.An open-field test is used to assess locomotor activity related to anxiety.Not many studies have analyzed the effects of quinpirole dosages on locomotor activity.The purpose of this study was to look at the locomotor activity of quinpirole-injected mice in an open-field test.Methods: The open-field test was used to observe the locomotor activities of 28 mice.Quinpirole was administrated at 0.05-5 mg/kg and normal saline were used as a control.The Mann-Whitney U-test was employed to compare the locomotor activities in the quinpirole and control groups.Results: Quinpirole-induced locomotor activities reduced as time elapsed during the first 30 minutes following the injection in most mice, then increased or fluctuated in the later 30 minutes.As the dosage was increased, there was a stronger initial inhibition, followed by a rapid and further increase in the last 30 minutes.Conclusion: This study showed the differential effects of quinpirole-induced locomotor activities depending on dosage, and initial suppression of locomotor activities by quinpirole was observed.Additionally, longitudinal observation of more than 1 hour would be required to look into the biphasic pattern of quinpirole in an animal model.