D-1 DOPAMINE-RECEPTOR AGONIST (SKF-38393) INDUCTION OF FOS IMMUNOREACTIVITY IN PROGESTIN RECEPTOR-CONTAINING AREAS OF FEMALE RAT-BRAIN

Injection of dopamine or dopamine receptor subtype agonists facilitate s the expression of lordosis in estrogen-primed female rats, The D-1 r eceptor specific agonist, SKF-38393, facilitates lordosis in estradiol -primed female rats via a process that requires progestin receptors, B ased on these data, neuronal response to the D-1 receptor agonist SKF- 38393 was assessed by expression of the immediate early gene protein, Fos. In the first experiment we examined the modulation of Fos express ion by D-1 agonists in progestin receptor-containing areas of estradio l-primed female rat brain, In the second experiment we examined if the re are progestin receptor-containing cells that respond to stimulation of D-1 receptors with increased Fos expression, Ten to 14 days follow ing ovariectomy and stereotaxic surgery, animals were injected with 5 mu g estradiol benzoate, Forty eight h later they were injected intrac erebroventricularly with 100 ng of SKF-38393 or saline. One h followin g injection animals were perfused, and brain sections immunostained fo r Fos protein, Results from the first experiment suggest that SKF-3839 3 increased the total number of Fos immunoreactive cells in the mid-ve ntromedial hypothalamic nucleus/ventrolateral portion (VMHVL), the cau dal VMHVL, the paraventricular hypothalamic nucleus and the caudate pu tamen. In the medial preoptic area, the rostral VMHVL and the arcuate hypothalamic nucleus, there was a significant increase in the number o f darkly stained Fos-immunoreactive cells following the SKF-38393 trea tment, In the second study, SKF-38393 increased the number of progesti n receptor-containing cells which contained Fos immunoreactivity in th e caudal VMHVL. The results suggest potential sites of action for the facilitation of sexual behavior by centrally administered D-1 agonists .