How these two peptides help manage autism

A new drug target may improve the social behaviour of autistic individuals. Using the mouse model, researchers have suggested this drug target based on a new understanding of what happens in an autistic brain that limits social behaviour (bit.ly/autism-disorder).

Autism comprises a spectrum of conditions that affect a person's social behaviour. While some individuals with autism are geniuses like Darwin, Einstein and Newton, others struggle to socialise and communicate. Genetic and environmental factors like prenatal exposure to chemicals cause the autism spectrum disorder, which affects 1 in 100 people in the world (bit.ly/autism-prevalence). But currently there is no cure and treatment involves managing symptoms via behavioural and psychological interventions, and speech and language therapies.

"Emerging studies have identified (the) neural circuit that governs social interaction. However, we know nothing about the neuromodulation of this circuit and how loss of fine-tuning of this circuit could lead to deficit in social interaction," says Sourav Banerjee of the National Brain Research Centre, who was not associated with the study.

In the past few years, researchers and clinicians have been testing if administering two peptides, oxytocin and vasopressin that are released in the brain, can improve social behaviour. While some studies showed positive effects, others concluded they don't work.

Oxytocin and vasopressin are being released but where are they going and what are they acting on, asks Prabahan Chakraborty, who is currently a Research Assistant Professor at the SRM Institute of Science and Technology and was formerly a post-doctoral candidate at Freddy Jeanneteau's lab at the University of Montpellier.

As part of the French team, he dissected how these neuropeptides act to induce social behaviour by studying what happens in the brain of lab mice and autistic mouse model during positive social interactions, like interest in a stranger and getting accustomed to a stranger after repeated interactions. They found that both oxytocin and vasopressin act on somatostatin neurons that are in the lateral septum of the brain.

Next, they found that in non-autistic mice, these peptides reduce the activity of these neurons, leading to their usual social behaviour whereas in autistic mice, the high activity of these neurons reduces social interaction. The team further showed that by reducing the activity of somatostatin neurons of the lateral septum with drugs in the autistic mice, there is an improvement in their social behaviour.

"This seminal study has shown that inhibition of activity of these neurons by interplay of oxytocin and vasopressin signalling could reverse the deficit in social interaction," adds Banerjee.