September 7, 1982

INJECTIONS of a synthetic substance made for studies of the chemistry of human emotion have produced severe anxiety in monkeys within seconds. The animals became agitated, their hair rose, they squirmed and they displayed other outward signs of extreme alarm. These effects could be quickly halted by other chemicals. Scientists have known for years that drugs such as the benzodiazepines Librium and Valium can lessen anxiety. But the ability to create such a pure state almost instantly with a drug alone is new and unexpected, according to scientists at the National Institute of Mental Health in Bethesda, Md. ''For the first time we may have a reasonable understanding of the biochemistry of anxiety,'' Dr. Steven M. Paul of the institute said recently. He referred not only to his own work, but a whole body of new research at many scientific centers.

International A decision to increase lending by the leading industrial countries to nations with acute debt problems was praised by Jacques de Larosiere, the top official of the International Monetary Fund. But, in opening the fund's annual meeting, he urged a speedy implementation of the program to ''assure the stability of the international financial system.'' (Page A1, Col. 6.) An Arab League conference opened in Fez, Morocco. The Arab leaders are expected to focus on the plight of the Palestinians after their military rout by the Israelis in Lebanon. (A1:3.)

The director of a leading pro-Israeli lobbying organization in Washington said today there was ''a lot of value'' in President Reagan's Middle East initiative. The lobbyist, Thomas A. Dine, the executive director of the American Israel Public Affairs Committee, openly differed with Prime Minister Menachem Begin and the Israeli Cabinet, which rejected the Reagan plan.. He said the key to its success would be whether Jordan agreed to join the Palestinian autonomy talks with Israel, Egypt and the United States. In an interview, Mr. Dine said that ''there were many constructive points'' in Mr. Reagan's plan and that ''it has been very well received by the American population.'' ''I can assume that members of Congress, who will be returning from recess to Washington this week, will also receive it in the same way,'' Mr. Dine said.

One expert on international affairs has an unorthodox proposal to slow the hand of any President who might be tempted to unleash a nuclear attack. It has long been feared that a President could be making his fateful decision while at a ''psychological distance'' from the victims of a nuclear barrage; that he would be in a clean, air-conditioned room, surrounded by well-scrubbed aides, all talking in abstract terms about appropriate military responses in an international crisis, and that he might well push to the back of his mind the realization that hundreds of millions of people would be exterminated. So Roger Fisher, professor of law at Harvard University, offers a simple suggestion to make the stakes more real. He would put the codes needed to fire nuclear weapons in a little capsule, and implant the capsule next to the heart of a volunteer, who would carry a big butcher knife as he accompanied the President everywhere. If the President ever wanted to fire nuclear weapons, he would first have to kill, with his own hands, that human being. ''He has to look at someone and realize what death is - what an innocent death is. It's reality brought home, '' says Professor Fisher.

Government officials and bankers attending meetings of the International Monetary Fund here fully recognize that the world financial system has been undergoing the greatest peril of the postwar period, but say they feel that the danger of a collapse has now been warded off. The apparent success of the United States and the International Monetary Fund in assembling rescue programs that have involved private banks as well as public institutions has encouraged the belief here that similar rescues would be conducted to prevent defaults by other debt-laden countries. However, there are are still worries about the adequacy of funds that can be made available to keep nations from insolvency. The potential list of casualties is long and the total of their foreign debts by the end of this year is likely to exceed $500 billion, with Mexico, at $81 billion, the biggest debtor.