The role of the ‘love hormone’ as a non-negotiable for social attachment is being questioned by research on the humble prairie vole.
A study published on Friday has shown that prairie voles – which mate for life – can still form attachments with their mates and be a caring parent without oxytocin, or the love hormone.
This contradicts forty years of research which suggested that oxytocin receptor signalling was an essential pathway for the development of social behaviours.
“We were all shocked that no matter how many different ways we tried to test this, the voles demonstrated a very robust social attachment with their sexual partner, as strong as their normal counterparts,” says University of California SF neuroscientist, Assistant Professor Devanand Manoli.
Prairie voles are monogamous, and male and female partners form ‘pair bonds’. These pairs will share parental responsibilities, groom each other, and generally seem to really like each other.
Previous studies had used drugs to block oxytocin from binding to its receptor, and found that voles were unable to pair-bond when oxytocin signalling was blocked.
However, when the team of researchers went more specific – using CRISPR to create prairie voles that lacked functional oxytocin receptors at all – they found that these CRISPR voles bonded just as much as normal voles.
The CRISPR voles also had very similar ability to give birth and nurse compared to their normal counterparts. Both male and female voles engaged in the usual parental behaviours of huddling, licking, and grooming, and were able to rear pups to weaning age.
However, the female CRISPR voles weren’t able to produce as much milk as regular voles, and the pups that survived to weaning age were smaller.
This result is different to some mice studies in which CRISPR was used, as well as drug studies in both voles and other animals. More research will need to be done to find out more.
“Drugs can be dirty,” says Manoli, “in the sense that they can bind to multiple receptors, and you don’t know which binding action is causing the effect. From a genetics perspective, we now know that the precision of deleting this one receptor, and subsequently eliminating its signalling pathways, does not interfere with these behaviours.”
More importantly, this study suggests that oxytocin might not be as crucial to human social bonding either.
“For at least the last ten years people have been hoping for the possibility of oxytocin as a powerful therapeutic for helping people with social cognitive impairments due to conditions ranging from autism to schizophrenia,” Manoli says.
“This research shows that there likely isn’t a magic bullet for something as complex and nuanced as social behaviour.”
The research has been published in Neuron.