Inhibiting Biosynthesis and Metabolism of Progestins in the Ventral Tegmental Area Attenuates Lordosis in Rats During Behavioral Estrus

The study investigated the role of 3α,5α-THP in the ventral tegmental area (VTA) in facilitating lordosis behavior in female rats. Researchers hypothesized that both the biosynthesis and metabolism of 3α,5α-THP are crucial for this behavior. In three experiments, naturally-receptive rats received VTA infusions of inhibitors (digitoxin and finasteride) to block the biosynthesis and metabolism of progestins. The results showed that these inhibitors significantly reduced lordosis and midbrain 3α,5α-THP levels, but not plasma levels, compared to a vehicle. However, infusions of 3α,5α-THP to the VTA restored lordosis and midbrain 3α,5α-THP levels after inhibitor administration. This suggested that both central biosynthesis and metabolism of progesterone to 3α,5α-THP in the VTA were important for mediating lordosis in rats.