The effect of Giprotein modification produced by intrastriatal pertussis toxin injection on dopcmine (DA)-mediated behaviors was studied. Administration of the selective D2agonist quinpirole induced ipsilateral rotation but the selective D1agonist SKF 38393 did not. However, SKF 38393 was able to increase the rotation induced by quinpirole. The selective D2antagonist raclopride and the selective D1antagonist SCH 23390 both blocked the effect of quinpirole. Striatal levels of cAMP were measured in both intact and pertussis toxin injected striatum. SKF 38393 induced a significant increase in cAMP, but quinpirole had no effect. When both drugs were administered together, quinpirole attenuated the SKF 38393-induced increase in cAMP levels. Moreover, quinpirole-induced attenuation of SKF 38393 effect was greater in intact striatum. In pertussis toxin-injected striatum, quinpirole only attenuated SKF 38393-induced increase of cAMP to control levels. This imbalance between intact and injected striatum might be the cause of the rotation in pertussis toxin-injected rats suggesting an important role for G proteins in DA receptor interactions. © 1991.
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