Laterality of dopamine function and neuroleptic action in the amygdala in the rat

Rats selected according to turn preference in an open field were categorised as showing left or right hemispheric dominance (turning to right or left respectively). Dopamine was persistently infused into the central area of the left or right amygdala of animals showing left or right hemispheric dominance. Infusion was effected for 9 days by Alzet osmotic minipumps, implanted subcutaneously, which delivered 25 micrograms/24 hr of dopamine via chronically-indwelling, stereotaxically-located injection units. Dopamine caused marked and consistent hyperactivity only when infused into the left amygdala when the right hemisphere was dominant. This hyperactivity developed during the first day of infusion and persisted throughout the 9-day infusion period. Both (-)sulpiride and fluphenazine, injected unilaterally into the amygdala, antagonised the hyperactivity caused by infusion of dopamine into the left amygdala in animals with right hemispheric dominance. This antagonism could be effected both from the infused amygdala [5-50 pg (-)sulpiride, 25-100 pg fluphenazine] and from the contralateral amygdala [100-250 pg (-)sulpiride, 25-100 pg fluphenazine]. Thus, a laterality was shown for the action of dopamine in the amygdala of the rat. In contrast, neuroleptic agents failed to show an exclusive laterality of action, but were able to act in either hemisphere to antagonise the effects of dopamine injected into the left amygdala. Interhemispheric biochemical differences "within-animals" could not be shown, although differences were seen between rats having right or left hemispheric dominance.(ABSTRACT TRUNCATED AT 250 WORDS)