Researchers used gene manipulation technology to remove the ‘P4h-tm’ gene from the mouse genome and found an unexpected change in mouse behaviour.
‘P4h-tm’ knockout mice showed striking courage and a lack of learned helplessness compared to congenic wild-type mice with a functional ‘P4h-tm’ gene.
The researchers assessed the mice with a large behavioural test battery that included a novel type of test for the panic reaction. The mice were placed in an air-tight box that was first filled up with regular room air and with 10 per cent carbon dioxide.
An elevated concentration of carbon dioxide induces an innate freezing reaction that is thought to resemble the feeling of suffocation in patients suffering from panic attacks.
‘P4h-tm’ knockout mice displayed substantially less freezing than control mice in response to carbon dioxide exposure. In tests for social interaction, ‘P4h-tm’ knockout mice made clearly more contact with another mouse than the controls.
.