Scientists have zeroed in on that part of the brain in women which could be the seat of heterosexual desire.
The study confirms that the hormone oestrogen is vital for arousal, but only in the specific area of the brain called the ventromedial nucleus (VMN) in the hypothalamus.
Sonoko Ogawa of the University of Tsukuba in Japan and her collaborators in the US discovered this by blocking the effects of oestrogen exclusively in that part of the brain in mice.
They used a harmless virus to shuttle the RNAs exclusively into the VMN, so that oestrogen signals would only be blocked there and nowhere else in the body. The effect was dramatic - the females refused to have sex.
“They became extremely aggressive towards males, and started biting and kicking when males approached,” says Ogawa. The females refused to mate and none of them showed the usual signs of sexual receptivity. By contrast, control females injected with neutral RNAs mated as usual. View a video of the normal mice (top) and those in which sexual receptivity was blocked (bottom).
“Disruption of normal oestrogen signalling only in this region while leaving it intact elsewhere in the brain and the rest of the body is sufficient to completely block normal female courtship behaviour,” says Ogawa.
She says that the VMN has long been suspected to be the seat of female desire, but experiments in mice genetically engineered to have no oestrogen receptor alpha anywhere in the body failed to prove this because they affected all receptors, not just those in the VMN. Blocking signals just in the VMN has now shown “unambiguously” that this is where female sexual behaviour is controlled, say the researchers.