Acetylcholine Concentrations in the Brain of Rabbits Exhibiting Forced Turning Movements

Abstract

Values for the free ACh concentration in the left and right cerebral cortex and caudate nuclei are given for normal rabbits as well as for animals exhibiting compulsive circling movements as a result of an unilateral (right) intracarotid injection of DFP. In animals exhibiting forced circus movements in either direction a marked asymmetry in ACh content existed between the left and right cerebral cortex as well as the left and right caudate nucleus. In rabbits circling to the left, the ACh content was higher on the right side in both the cortex and caudate nucleus. However, in rabbits turning compulsively to their right, the left cortex had a higher ACh concentration than the opposite side. In the case of the caudate nuclei, the right side was higher than the left. Since previous ChE data as well as the present ACh data for the caudate nuclei in ‘righters’ and ‘lefters’ show little difference it is difficult to implicate the caudate alone in the mechanism of compulsive turning. It is thought that the caudate nucleus may be involved in a secondary manner in the production of rabbits circling to the left. However, the biochemical evidence does suggest that stimulation due to the accumulated ACh on one side of the cerebral cortex may be the primary factor in causing the animal to exhibit compulsive circling toward the contralateral side.