Effects of dopamine agonists and antagonists on optical responses evoked in rat frontal cortex slices after stimulation of the subcortical white matter
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Effects of dopamine agonists and antagonists on the optical response of frontal cortical slices to stimulation of the subcortical white matter were examined using a voltage-sensitive dye and a high-speed image sensor. In the slices treated with bicuculline, stimulation of the white matter evoked optical responses propagating to the overlaying cortex. Bath application of the D1 agonist, chloro-APB (1 µM), consistently decreased the intensity of the early part of the response but increased the duration of the response occurring at the superficial layers of the cortex. Application of the D1 antagonist, SCH 23390 (1 µM), resulted in a small increase in both the intensity and the duration of the response. Bath application of the D2 agonist, quinpirole (1–10 µM), reduced the response occurring after 10 ms from stimulation. The effects of chloro-APB and quinpirole were additive. Application of the D2 antagonist, eticlopride, did not cause a significant change in the response but effectively blocked the quinpirole effects. This study suggests that although both D1 and D2 agonists reduced the peak optical response evoked in the slices of the frontal cortex, the two agonists exerted different temporal and spatial effects.
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