Brain structures involved in the sexual behaviour of Ile de France rams with different sexual preferences and levels of sexual activity

Abstract

Using Fos, as a marker, we analysed the brain structures of rams, with different libidos or sexual preferences that had been activated by contact with males or females. Ile de France rams aged from 1.5 to 7 years were used. Fos immunoreactivity (Fos IR) was analysed in rams with high (HL) or low libido (LL) after 90 min of direct contact with females (HL DirF n = 7 or LL DirF n = 7) or in rams of high libido having indirect contact through a fence, with females (HL IndF n = 6) or males (HL IndM n = 5) and finally, in males who preferred other males as partners by indirect contact through a fence with males (MO IndM n = 4). Direct or indirect contact with a preferred sexual partner (LL DirF, HL Dir F, HL IndF, MO IndM) induced the appearance of Fos-IR cells in several diencephalic and cortical structures. Conversely, indirect contact with males did not induce Fos-IR in males interested in females (HL IndM). In the medial preoptic area (MPOA), the paraventricular nucleus and the medial bed nucleus of the stria terminalis the cell density of Fos IR cells was higher in HL Dir F than in LL DirF suggesting involvement in sexual motivation whereas only the MPOA seemed involved the consummatory component of sexual behaviour (Fos IR density HL DirF > HL IndF). The enthorinal cortex was the only structure specifically activated by males attracted to other males (Fos IR density MO IndM > HL IndM) whereas Fos IR density did not differ between the HL IndF and HL IndM groups.