Fig 6. Blocking neuronal activity in genital cortex prevents area growth and delays female sexual maturation.

(A) Prepubescent animals (postnatal day [P]23) received Ringer impregnated Elvax sheets above genital cortex and were cohoused together with a sexually experienced adult male for 7 days. (B) Same as (A), but Elvax implants released tetrodotoxin (TTX), which blocked neuronal activity in genital cortex. (C) Outline of a somatosensory cortex (S1) map from the brain of a P30 female, who received a ringer soaked implant above genital cortex and was cohoused with a sexually experienced adult male. Genital cortex is depicted in black. (D) Same as (C), but example map stems from the brain of a P30 female, whose genital cortex was blocked through a TTX containing implant. (E) Absolute area of clitoris representation in hemispheres of P30 females, which were cohoused with sexually experienced adult males and received beforehand either Elvax implants containing Ringer or TTX. Note that genital cortices in Ringer treated animals show significant larger growth compared with animals that received TTX implants above genital cortex. (F) Same as (E), but the fraction of genital cortex of the S1 is plotted. (G) Same as (E), but the absolute area of S1 is shown for the 2 groups. There is no difference in S1 size. (H) Pictures of clitoris and vagina taken before implanting animals with Ringer containing Elvax sheets (P23) and after cohousing them for 7 days with sexually experienced adult males. Note that the vagina was already open at P30. (I) Same as (H), but pictures show clitoris and vagina of an animal, who received a TTX-soaked Elvax implant above genital cortex. The vagina stayed closed when blocking genital cortex, while cohousing the prepubescent animals with a sexually experienced adult male. (J) Mean scores for vaginal opening. A score of 0 represents a closed vagina, whereas a score of 1 stands for an opened vagina. The intermediate state (between open and closed vagina) has a score of 0.5. The majority of females, which received a Ringer soaked implant above genital cortex, showed either an opened vagina or a half opened vagina, which was about to open after being cohoused for 7 days with sexually experienced adult males. In contrast, almost all animals implanted with TTX Elvax sheets had the vagina closed at P30. Each dot represents the score of vaginal opening for 1 animal. (K) Uterine weights of females with implanted Ringer or TTX Elvax sheets after being cohoused with sexually experienced adult males. No significant difference (P = 0.93, Student t test) was found between the groups. See also S1 Data.