Amygdala kindling modifies interhemispheric dopaminergic asymmetry

Brain dopamine is known to retard the development of kindled seizures, but it is uncertain whether kindling affects dopamine function. In the present study, rats were screened for cerebral dominance by recording their preferred direction of rotation when injected with d-amphetamine. Bipolar stimulating electrodes were then implanted in the amygdaloid complex of either the dominant or nondominant hemisphere (i.e., respectively, contra- and ipsilateral to the preferred direction of rotation; the dominant hemisphere identified in this way has been shown to contain higher concentrations of dopamine than the nondominant hemisphere). Kindling stimulation (or sham-kindling, in control rats) was applied through the electrodes two or three times daily for 21 days, and the rats were reassessed for amphetamine- and apomorphine-induced rotation, during and after the course of treatment. Kindling of the originally dominant hemisphere caused a diminution of rotational asymmetry as measured in tests 2 to 3 h after stimulation sessions, and in some rats led to a reversal in the preferred direction of amphetamine-induced rotation. Kindling of the nondominant hemisphere tended to accentuate the original amphetamine-induced asymmetry. The direction of rotation induced by a direct postsynaptic DA-receptor agonist (apomorphine) was not significantly affected by kindling of either hemisphere. It appears that kindling stimulation brings about a relatively inferior level of DA function on the stimulated vs. the nonstimulated side of the brain, and that this process depends mainly on changes occurring at a presynaptic level.