Dependence of dopamine receptor conversion from agonist high- to low-affinity state on temperature and sodium ions

Previous workers found that the anterior pituitary dopamine receptors were inconsistent in converting from their high-affinity state (D2 high) into their low-affinity state (D2 low) for dopamine. We tested, therefore, whether temperature or sodium ion concentration could be factors accounting for such inconsistencies. We found that the proportion of sites which converted depended on the temperature of incubation. No conversion occurred at 4 degrees, despite the presence of guanine nucleotide and sodium ions. At room temperature (20 degrees) guanine nucleotide consistently induced complete conversion in the presence of sodium ions, but gave inconsistent conversion in the absence of sodium ions. At body temperature (37 degrees) guanine nucleotide consistently resulted in complete conversion without requiring sodium ions.