Brain findings may help unravel autism mystery

WASHINGTON - Pleasure receptors best known for helping the body respond to morphine and opium may also hold the key to mother-child bonding, scientists report.

Mice pups genetically engineered to lack these receptors - known as doorways into cells - were unable to properly bond with their mothers. They did not show natural distress when separated from them, reported the researchers in Friday's issue of the journal Science.

They say it may be that children with so-called attachment disorders - most notable in autism - lack properly functioning opioid systems.

With colleagues, Francesca D'Amato of the CNR Institute of Neuroscience, Psychobiology, and Psychopharmacology in Rome used mice with no mu-opioid receptor - a protein vital to the brain's pain circuitry.

Normal baby mice, when separated from mothers, will squeal, especially if put into a strange environment.

But the mutant mice barely whimpered when this happened. It was not from lack of fear - the mutated babies whimpered and squealed just as much as normal pups when put into a cold beaker.

Francesca D'Amato said the experiment supported a theory that pleasure and bonding are linked. The opioid system may help babies bond with mothers by associating the smell of their mother with pleasure.

If research supports this, the mutant mice could help in the study of human autism and other attachment disorders, they said.

- REUTERS