Role of MT1/MT2 receptors in the melatonin-induced expression of MT1 and MT2 (A), production of progesterone (B), STAR protein and mRNA expressions (C, E), and LHR protein and mRNA expressions (D, F) in the TI in small follicles. Small follicles were treated with 10 ng/mL melatonin alone or in combination with MTR inhibitors, 10 μM luzindole, or 10 μM 4P-PDOT for 48 h. Total RNA was extracted from the TI. The mRNA expressions of MT1, MT2, STAR, and LHR were measured by RT-qPCR. GAPDH expression was used as a standard. Progesterone concentration was measured by ELISA. TI lysates were subjected to SDS-PAGE/immunoblotting for STAR, LHR, and GAPDH analyses. The relative density ratio was calculated using a control group value of one. The results are the mean ± SEM of three independent experiments. *P < 0.05, **P < 0.01.