Glucocorticoid status affects the response of rat striatal dopamine D2 receptors to hyperthermia and turpentine treatment

The influence of glucocorticoid status of the rats (absence of glucocorticoid hormones achieved by adrenalectomy and substitution by dexamethasone 5 mg/kg b.w.) on the response of striatal dopamine-D2 receptors to environmentally induced hyperthermia and treatment with a local inflammatory agent turpentine (1 ml/kg b.w.) was studied. Both stress situations affected the density of D2 receptors in opposite directions. While hyperthermia led to an increase, turpentine treatment reduced Bmax value. The changes in the D2 receptor binding affinity were expressed as a certain decrement, which was statistically significant in sham-adrenalectomized hyperthermic animals and in both turpentine treated groups (sham-operated and adrenalectomized) administered dexamethasone. The absence of glucocorticoids in the circulation caused an elevation of Kd values in the control and both stressed groups and dexamethasone attenuated these changes. Dexamethasone also attenuated stress-related alterations of Bmax, as well as Kd increase upon adrenalectomy in control and hyperthermic animals. These results corroborate the evidence on the role of D2 receptors in thermoregulation and stress and demonstrate the significance of glucocorticoid hormones in the control of these processes.