Singer, Jay J.

Twenty-six 75-day-old, ovariectomized Long-Evans female
rats were randomly divided into two groups of ten and one
group of six animals. The ten Group I Ss received, in consecutive
treatment periods, 2 mg progesterone (P-2) daily,
2 mg testosterone propiorate (TP-2) daily, TP-2 daily plus
P-2 every fourth day, and P-2 every fourth day. The ten Group
II Ss received, in consecutive treatment periods, P-2 every
fourth day, and 4 mg dihydrotestosterone (DHT-4) daily plus
P-2 every fourth day. Both Groups I and II were tested for
female sexual behavior. A significant increase in the lordosis
response was observed only in Group I Ss after receiving TP-2
plus P-2 every fourth day. Group III Ss were tested for male
sexual behavior after receiving DHT-4 daily. Male sexual
behavior increased significantly after DHT-4 treatments. It
was concluded that progesterone exerts a facilitatory effect
on female sexual behavior only when the Ss have been previously
primed with an aromatizable androgen and that dihydrotestosterone
is capable of inducing male sexual behavior in female rats.

Fourteen 75-day-old female rats of the Long-Evans strain
were ovariectomized and divided into two groups of seven.
Group I received daily injections of 2mg testosterone propionate
(TP) and was tested for male sexual behavior. Group
II, in addition to daily injections of TP, also received injections
of 1mg progesterone on five of the ten test days.
This group was tested for female sexual behavior. TP was
found to exert a facilitory effect on both male and female
sexual behavior. Female sexual behavior was enhanced
further when progesterone was administered 4 to 6 hours
prior to testing. Progesterone, when injected alone, was
found to induce lordosis. It was concluded that TP was
first being converted to estrogen and it was the estrogen
which was responsible for the increase in female sexual
behavior. The fact that progesterone, which enhances
estrogen-induced lordosis, also enhances testosterone-induced
lordosis supports this position.