Effect of estradiol and progesterone on rat striatal dopamine uptake sites

Abstract

Striatal dopamine (DA) uptake sites labelled with [ 3H]GBR-12935 binding were investigated in ovariectomized (OVX) rats acutely treated with 17β-estradiol (E 2) or progesterone (P). One injection of E 2 (100 ng, SC) to OVX rats increased plasma levels of this steroid after 15 min while plasma prolactin (PRL) levels remained unchanged. The E 2 injection left striatal [ 3H]GBR-12935 binding affinity unchanged while the maximum density increased 15 and 30 min after the injection (+ 24% and +18%, respectively). One injection of P (110 μg, SC) to OVX rats increased this steroid plasma level from 15 to 120 min while plasma PRL levels remained unchanged. [ 3H]GBR-12935 binding density and affinity remained unchanged up to 120 min after the injection. Thus, acutely, E 2 but not P, modulated striatal DA uptake sites in OVX rats. The effect of E 2 appeared in coincidence with the peak of this steroid plasma concentration. This increase was rapid and is probably nongenomic and suggests a causal effect relationship as well as a presynaptic site of action of E 2.