Autoradiography of dopamine receptors and dopamine uptake sites in the spontaneously hypertensive rat

Abstract

We examined the status of dopamine (DA) D 1 and D 2 receptors by using [ 3H]SCH 23390 and [ 3H]spiperone binding, respectively, and DA uptake sites by using [ 3H]mazindol binding in spontaneously hypertensive rats (SHR) and Sprague-Dawley (SD) rats. SHR showed significantly higher [ 3H]SCH 23390 and [ 3H]spiperone binding in the caudate-putamen (CPu), the nucleus accumbens (NAc) and the olfactory tubercle (OT) in comparison to the SD rats. There were no significant differences in [ 3H]mazindol-labeled DA uptake sites between the two strains. Unilateral 6-hydroxydopamine (6-OHDA) injection into the striatum resulted in more than 90% depletion of DA uptake sites in the CPu in both strains. 6-OHDA-induced DA depletion was associated with significant increases in striatal [ 3H]spiperone binding which were of similar magnitude in the SD rats (+64.1%) and SHR (+51.3%). There were only small decreases (−5.4%) in D 1 receptor binding in the dorsolateral aspect of the CPu in the SHR, whereas there were no changes in striatal D 1 receptors in the SD rats. These results indicate that, although the SHR have higher concentrations of both D 1 and D 2 receptors in the basal ganglia, these receptors are regulated in a fashion similar to DA receptors in SD rats after 6-OHDA-induced striatal DA depletion.