Postpartum anixety research – provides real benefits for NZ mothers
Dr Caroline Larsen
On-farm research could provide a crucial step in linking University of Otago postpartum anxiety research to real benefits for New Zealand mothers.
Dr Caroline Larsen in the Anatomy department is looking into the causes of postpartum mood disorders, commonly referred to as postnatal depression.
At present, postpartum mood disorders are poorly understood and difficult to treat. Dr Larsen hopes that understanding the mechanisms that lead to the disorder will help with the development of more effective preventative medicine and treatments.
The answer may lie with hormonal levels during pregnancy. Levels of prolactin, the hormone responsible for enabling breastfeeding (among other roles), increase dramatically during pregnancy. Prolactin stimulates neurogenesis (the generation of new cells, or neurons) during pregnancy. In mice, Dr Larsen has shown that the level of neurogenesis in the mother during pregnancy affects levels of anxiety and the way she behaves to her offspring after she has given birth.
The mouse trials have signalled some promising developments, and similar results with a larger animal will take this success to the next level. Not only is the sheep closer in size to humans, it is more similar in ovarian function and hormonal activity.
“We’ve previously shown in mice that decreasing prolactin in the early stages of pregnancy increases anxiety, but we want to look in another animal model to replicate that data.”
She says that conversations at a past Centre for Reproduction and Genomics Colloquium and generous assistance from fellow scientists have allowed two research programmes to come together to maximise resources, with the sheep being used for two different studies simultaneously.
As a part of a separate study, Dr Peter Hurst of Anatomy and Peter Smith of AgResearch are conducting a trial on an Invermay flock to investigate the link between maternal testosterone levels and Polycystic Ovarian Syndrome in female lambs. Ewes are treated with testosterone throughout the gestation period, with blood samples taken fortnightly and compared with those taken from a control flock.
For the postpartum anxiety trial, blood samples will be tested for levels of the entire range of hormones present to identify fluctuations: testosterone, progesterone, oestrogen, cortisol, placental lactogens and prolactin.
The lambs are due to be born in January, and this is when the hormonal profile information will be matched with behavioural testing. It is anticipated that the flock treated with testosterone will demonstrate impaired maternal function and possibly be more anxious. Measuring anxiety and maternal behaviour in animals is a separate challenge in itself, and Dr Larsen is drawing on assistance from AgResearch’s Dr Anne O’Connell and Dr Julie Everett-Hincks for knowledge about sheep behaviour.
“The sort of maternal behaviours we might identify could be bleating when the lamb is taken away, or seeing whether both the ewe and the lamb seek each other when they are apart,” says Dr Larsen.
Finding a clear way to improve maternal behaviours could also lead to knowledge that would help farmers improve lamb survival rates. Sheep are naturally affected by differing levels of maternal function, with some shunning lambs or allowing them to be ‘adopted’ by other ewes.
