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Mother mouse's 'love' like a drug: study

WASHINGTON - Mice lacking morphine receptors in the brain were unable to bond properly with their mothers, scientists found, which may provide a clue to the roots of such diseases as autism.

Normally, baby mice will squeal frantically when separated from their mother. But Italian researchers genetically engineered a group of mice to lack a key opioid receptor in the brain that is best known for its role in pain, pleasure and addiction.

Francesca D'Amato of the CNR Institute of Neuroscience, Psychobiology, and Psychopharmacology in Rome and colleagues found the opioid-receptor deficient pups hardly cried compared to normal mice.

When the researchers gave the normal pups the opioid drug morphine, it reduced the distress. But when they gave it to the mutant mice, it didn't appear to have an effect.

The mutated mice did squeal, though, when they were placed in a cold beaker or smelled a threatening male, which shows they had a normal response to fear. Pups fear strange males who may see them as lunch.

The findings may support the theory the brain's opioid pathway is linked to attachment.

"Results from this study may indicate a molecular mechanism for diseases characterized by deficits in attachment behavior, such as autism or reactive attachment disorder," the researchers wrote in Friday's issue of the journal Science.

People with autism have difficulty interacting and communicating with others.

If people with autism are found to have opioid systems that don't work properly, then the mice could offer a model for studying the human disorder.

Posted by thinkum at June 30, 2004 12:53 PM