Kiss1 is expressed outside the hypothalamus in the amygdala in rodents, a recent study reveals.

Kisspeptin—a neuropeptide encoded by the Kiss1 gene—is a major regulator of puberty and fertility. Kiss1 expression in the brain has been found in two discrete areas of the hypothalamus and each hypothalamic population has different functions in the regulation of reproduction. However, “by chance, during one of our previous studies in rodents, we noticed a third novel population of Kiss1-expressing neurons in the amygdala region,” says senior researcher Alexander Kauffman of the University of California San Diego.

The investigators used radiolabeled in situ hybridization to localize the expression of Kiss1 in the amygdala of the brains of mice and rats and find out whether Kiss1 expression in the amygdala was regulated by sex steroids. In both species, Kiss1 was expressed in the medial amygdala and was more highly expressed in males than females. The Kiss1 neurons in the medial amygdala were regulated by circulating levels of sex steroids in both males and females, which seemed to occur by an estrogen-receptor-dependent pathway.

“Our new findings suggest that kisspeptin signaling in the brain may also be arising from extra-hypothalamic regions, such as the amygdala, though this needs to be verified for humans as we have now shown for rodents. Drugs and manipulations targeting Kiss1 neurons will have to consider possible actions in the amygdala in addition to previously known hypothalamic regions,” concludes Kauffman.