Figure 1. Real-time RT-PCR of 5 µg total RNA extracted from the periaqueductal gray of adult virgin (A, B, C) and lactating female rats (D, E, F) in relation to expression of Oprm1, Oprk1 and Oprd1. Data are reported as means ± SEM. ^*P < 0.05 compared to the blank group (ANOVA).