Publication highlights

Researchers at the Crick have found that hunger can make virgin female mice aggressive towards pups, but only in certain hormonal states. These mice would usually ignore other females' pups or show parent-like caring behaviour. The team found that AgRP neurons mediated the effect of food deprivation on behaviour towards pups, by targeting the medial preoptic area. Mice at certain stages of the reproductive estrous cycle were more likely to become aggressive towards pups, dictated by the ratio of oestradiol and progesterone setting the responsiveness of MPOA neurons. They showed that hunger information carried by the AgRP neurons dampens neuronal activity in the MPOA, stimulating the switch from caring behaviour to pup-directed aggression. 

Researchers at the Francis Crick Institute have shown that mice use chemical cues, including odours, to detect the social rank of an unfamiliar mouse and compare it to their own, using this information to determine their behaviour. They used a test where male mice enter a transparent tube at opposite ends, meeting in the middle. In this type of confrontation, a more submissive animal will typically retreat. Interactions between mice in the same cage were first used to rank each mouse, before observing that strangers could observe each other's rank and act accordingly. Putting the mice in the dark or removing their sex hormones had no impact, but when the researchers blocked the two chemosensory systems mice use, they could no longer recognise opponent rank, showing that both systems are used for rank recognition and can compensate if one is missing.

Researchers at the Francis Crick Institute have shown that pregnancy hormones ‘rewire’ the brain to prepare mice for motherhood. Their findings show that both oestrogen and progesterone act on a small population of neurons in the brain to switch on parental behaviour even before offspring arrive. These adaptations resulted in stronger and more selective responses to pups. They found that a population of nerve cells (galanin-expressing neurons) in an area of the brain called the medial preoptic area (MPOA) in the hypothalamus, associated with parenting, was impacted by oestrogen and progesterone. Brain recordings showed that oestrogen simultaneously reduced the baseline activity of these neurons and made them more excitable, whereas progesterone rewired their inputs, by recruiting more synapses (sites of communication between neurons. Making these neurons insensitive to hormones completely removed the onset of parental behaviour during pregnancy.