Figure 6.

Sexual dimorphism in hypothalamic kisspeptins. Kisspeptin (KP) neurons are located in two major regions: the arcuate (ARC) nuclei, and the anteroventral periventricular and periventricular preoptic nuclei (AVPV/PEN). KPR are expressed on the GnRH neurons. KPs expressed in hypothalamic nuclei are crucial for the onset of puberty, gonadal development, and maintenance of reproductive functions. Sex-specific differences in the numbers of KP neurons and the KP expression levels exist in the hypothalamus. KP neurons in ARC nuclei generate pulsatile GnRH secretion, while those in the AVPV nuclei induce the preovulatory gonadotropin surge (thick line). GnRH neurons, found near the pituitary gland, is innervated by the KP neurons of ARC and AVPV origins. While the KP expression in the ARC nuclei is similar between males and females, KP expression is highly dimorphic in the AVPV nuclei due to greater numbers of KP neurons in females. Thin lines stand for lower levels and thick lines stand for higher levels of expression.