Three "Silver Spring monkeys," the primates that became a cause celebre for the animal rights movement, were euthanized yesterday in a laboratory in Louisiana.

The death of the monkeys ended a chapter in a bitter, decade-long political and legal battle over research policy that has pitted federal officials and scientists against animal rights activists. Over the years, both sides have gone to extraordinary lengths to buttress their positions, and that intensity continued this week.

William F. Raub, the acting director of the National Institutes of Health, had asked two scientists to fly to Tulane University's Delta Regional Primate Research Center Thursday night to perform an experimental procedure that involved removing the tops of the monkeys' skulls and probing their brains with electrodes.

The decision to begin the experiment came on the heels of two legal setbacks for the animal rights groups. On Tuesday, the U.S. Court of Appeals here denied an appeal by the Physicians Committee for Responsible Medicine to temporarily block the procedure. Thursday night U.S. District Judge John Garrett Penn also denied their request for a preliminary injunction on the procedure.

The struggle over the monkeys began in 1981 when police raided an NIH-funded lab in Silver Spring and discovered several dead and diseased monkeys. The 17 crab-eating macaques that were rescued from the lab soon became known as the "Silver Spring monkeys," a rallying point for the fledgling animal rights movement.

Four of the monkey survivors are in Louisiana and five are in San Diego.

Peter Jerone, director of the Delta Regional Primate Center, said three monkeys in the experiment have been deteriorating for two years and researchers had been "magnanimous" in delaying the procedure until this week's court cases were decided.

Alex Pacheco, spokesman for People for the Ethical Treatment of Animals, a prominent animal rights group, called this explanation an "outrageous lie." He said NIH refused to allow independent veterinarians examine the monkeys.

Greg Simon, staff director for the investigations subcommittee of the U.S. House Science and Technology Committee, said the procedure also violates an agreement NIH made to delay experimentation until it met with congressional leaders.

Raub issued a statement late yesterday denying there was such an agreement. He also said in an interview that he issued the order because he had a "scientific obligation."

Yesterday morning's experiment was designed to investigate "remapping" in the brain. The results are supposed to be helpful in research on physical disability.

On Monday, PETA plans to protest the experiments by erecting a 12-foot metal and acrylic statue in front of the Department of Health and Human Services headquarters. The statue will portray a primate sacrificed on a "steel altar of science," the group said.