Scientists said Thursday they had discovered a brain protein that appears to be a target for a recently developed anti-schizophrenia drug, a finding that could aid development of better medications.

The protein may be useful in finding medications that retain the benefits of the drug while avoiding its side effects, scientists said.The drug is called clozapine. It is considered an advance because it helps some schizophrenics for whom standard drugs have failed and because it largely avoids movement disorders that can arise in users of standard drugs.

But clozapine carries its own side effects, especially the risk of a potentially fatal blood disorder called agranulocytosis. The problem develops in 1 percent to 2 percent of users, and patients must take weekly blood tests to check for it.

Clozapine went on the market in the United States last year.

The new research is presented in Thursday's issue of the British journal Nature by scientists at the University of Toronto, the Clarke Institute of Psychiatry in Toronto, Ontario, Canada, and the Oregon Health Sciences University in Portland.

The researchers said they cloned the gene for the protein and studied the protein's behavior in laboratory tests. They found that clozapine bound to it in the test tube.

The protein, called D4, belongs to the brain's family of dopamine receptors. The receptors receive bursts of a chemical called dopamine from neighboring brain cells as a key step in cell-to-cell communication.