Chemical structure of corticosteroids and its relationship with their acute induction of lordosis in the female rat.

The intravenous injection of several corticosteroids in the spayed estrogen-primed rat resulted, 5 min later, in a remarkable induction of lordosis response for deoxycorticosterone and 11-deoxycortisol. A lower but important effect was induced with corticosterone and 17 alpha-hydroxyprogesterone. A chemical structure-biological effect analysis showed that C-21 hydroxylation (e.g., deoxycorticosterone, 11-deoxycortisol, and corticosterone) induces the behavioral effect. However, C-11 or C-17 hydroxylation alone promotes the lordosis response to a lesser degree (corticosterone and 17 alpha-hydroxyprogesterone, respectively). However, the effect of these latter compounds is significant. From the results, it is concluded that deoxycorticosterone and 11-deoxycortisol along with other steroids such as 20 alpha-hydroxyprogesterone are suitable candidates for synergizing the well-known estrogen-progesterone induction of lordotic behavior.