Dopaminergic and non-dopaminergic circling activity of mice

Abstract

Male ICR albino mice kept in a closed space tend to rotate and have a preferred direction of rotation, which is more often to the left (65%) than to the right (35%). This circling asymmetry was measured with a rotometer in a group of animals following administration of various drugs. Morphine, amphetamine, apomorphine, atropine and pentylenetetrazol caused hyperactivity which was maximal for morphine and decreased in that order. All the drugs also increased the rate of rotation and the percentage of turning in the preferred direction, the latter again being maximal for morphine and decreasing in the order morphine, atropine, amphetamine, apomorphine, pentylenetetrazol. The dopaminergic agonists amphetamine and apomorphine also increased several-fold the rate of turning in the non-preferred direction, but this effect was much less obvious for the other drugs. Our results do not support a previous suggestion that rotational asymmetry is related to dopaminergic asymmetry in the brain. While the rotational asymmetry is influenced by the degree of activity of the animals, other unidentified factors are operating.