Effects of septal lesions and testosterone on lordosis behavior and luteinizing hormone release in female rats

The increased behavioral sensitivity to estrogen following a septal lesion in female rats has previously been found to be blocked by chronic treatment with testosterone propionate (TP) following the lesion. The effects of this chronic treatment on the ability of progesterone (P) to facilitate the secretion of luteinizing hormone (LH) in the spayed septal lesioned rat primed with estradiol benzoate (EB) was tested in the present study. EB was injected and followed 72 hr later with an injection of P. Blood samples for measurement of plasma LH were taken at 1700 hr, 29 and 53 hr after EB and 5 hr after P injection. Although there was no effect of the lesion, TP treatment significantly inhibited LH values after P administration. In a second experiment, spayed septal lesioned or sham operated rats were given either 0.0, 0.5 or 2.0 μg EB followed by 0.5 mg P just 24 hr later. The display of lordosis behavior, tested 4–6 hr after P injection, was significantly greater in septal lesioned than in sham operated rats following priming injections of 0.5 or 2.0 μ EB. This indicates that septal destruction significantly shortened the duration required for estrogen to prepare neural mechanisms for the effect of progesterone on lordosis behavior. Following a similar steroid regime, no differences were found between lesioned and sham operated rats in plasma LH levels in blood samples taken 5 hr after EB or 5 and 29 hr after P injection.