The American and Soviet cochairmen of International Physicians for the Prevention of Nuclear War accepted the Nobel Peace Prize today amid continuing controversy about their group and protests outside the award ceremony over the Soviet recipient.

Dr. Bernard Lown, professor of cardiology at the Harvard School of Public Health, and Dr. Evgeni Chazov, Soviet deputy health minister and a leading Moscow heart specialist, received the $230,000 award at a formal ceremony in the main hall of Oslo University. Security was tight and police kept protesters away from the entrance.

Both, in accepting the prize, implored their governments to stop nuclear tests. "From this world podium we call upon the governments of the United States and the Soviet Union to agree to an immediate mutual moratorium on all nuclear explosions, to remain in effect until a comprehensive test ban treaty is concluded," said Lown.

Lown said the movement's 135,000 doctors and health professionals strongly believe that the perpetuation of nuclear tests "has a central role in the development of new, more sophisticated and more destabilizing weapons."

Lown and Chazov cofounded the group informally known as Doctors Against Nuclear War in 1980 after developing a close friendship through joint medical research.

This year's award has aroused controversy because the group's goals coincide with present Soviet arms policy and because of revelations that Chazov signed a letter denouncing Andrei Sakharov, the dissident Soviet physicist and 1975 Nobel Peace Laureate, for allegedly slandering his country and committing "blasphemy" against peace.

A news conference yesterday at which the two health specialists faced hostile questioning on both issues came to an abrupt end when a Soviet journalist collapsed with a heart attack and both men rushed to his aid, apparently saving his life.

Dr. Erik Myhre, at the hospital where the Russian Lev Novikov is being treated, said, "His condition is no longer considered critical." The Associated Press said Novikov, 61, spoke by phone with his wife in Moscow.

Outside the university hall today, demonstrators hoisted signs reading "Free Sakharov," and "Find New Friends, Dr. Lown."

A nuclear moratorium, Lown said in his acceptance speech, "is verifiable, free of risk to either party, simple in concept yet substantive, has wide public support and is conducive to even more dramatic breakthroughs," he said.

Chazov said the doctors' "prescription for survival" included a test ban, a freeze and eventual elimination of nuclear weapons, a no-first-use pledge and preventing the arms race from spreading to outer space.

Lown and Chazov have rebuffed critics by insisting that their organization can only maintain its global consensus by publicizing the medical and environmental hazards of nuclear conflict and by keeping politically sensitive topics off its agenda.

"We are not indifferent to other human rights and hard-won civil liberties," Lown explained today. "But first we must be able to bequeath to our children the most fundamental of all rights . . . the right to survival."

Chazov, a member of the Soviet Communist Party's Central Committee, noted in his speech that the five years since the group's creation "were not all roses. We had to cope with mistrust, skepticism, indifference and sometimes animosity."

But he did not allude to any specific disputes over human rights issues or Sakharov's plight.

Egil Aarvik, chairman of the Norwegian Nobel Committee, mentioned in his opening address that the award has often been granted to human rights campaigners. He said the committee follows "the fate of these prize winners with interest" but emphasized that this year's focus on disarmament embraces "every human being's birthright."

Aarvik praised the doctors for informing the public about the nuclear threat with detailed scientific evidence about "the atomic winter, with its destruction of the biosphere and all conditions necessary for life." He also lauded their appeal that money for weapons should be invested on coping with hunger and inadequate health care around the world. Lown and Chazov also expressed hope that the doctors' movement will inspire their governments to embark on a new era of dialogue and detente.

"Confrontation is the road to war, destruction and the end of civilization," the Soviet physician said. "Cooperation is the road to increased well-being of peoples and the flourishing of life."

Lown underscored the notion that the doctors had succeeded where their governments, at least in recent years, had failed. While observing that the summit meeting last month in Geneva between Soviet and American leaders had generated some optimism, he said the rival superpowers must not only engage in attestations of good faith.

"Hope without action is hopeless," Lown said. "Our enthusiasm for the positive spirit in these deliberations [at Geneva] must not blind us to the absence of genuine progress toward disarmament."

Lown claimed 70 nuclear bombs were added weekly to arsenals.