Effects of intrastriatal hormones on the dorsal immobility response in the rat

Previous research has shown that the dorsal immobility response (DIR) changes significantly in duration across the estrous cycle. In order to test whether gonadal steroid hormones act directly on the striatum to modulate this behavior, ovariectomized female Long-Evans hooded rats were given bilateral intrastriatal implants of 17 beta-estradiol, 2-hydroxyestradiol, progesterone, or cholesterol. These implants were made at one-week intervals, each animal receiving each treatment in a Latin square design. Four hours after each hormone implant, the animals were tested for the DIR. Only rats receiving the intrastriatal 17 beta-estradiol implant were significantly different from those receiving cholesterol, and showed greatly potentiated DIR's.