What was going on when I was born?

Sharply contrasting views of Joseph M. Margiotta were presented today by opposing counsel as his trial on charges of mail fraud and extortion began in Federal District Court here. The 53-year-old Nassau Republican leader was portrayed by Larry J. Silverman, an assistant United States attorney, in his opening statement as a politician who ''lined the pockets of his faithful supporters and lined his own pockets to the detriment of the people of Nassau County.'' Mr. Silverman depicted Mr. Margiotta as the mastermind, ''the one calling the shots,'' in a scheme to kick back insurance premium commissions from Hempstead Township and Nassau County to Republican politicians designated by Mr. Margiotta. The politicians did little or no work for the commissions.

AFTER years of debate, a growing number of psychiatrists and psychologists are concluding that even children can suffer from depression. Clinicians had long insisted that children under about 14 years of age lack the psychological capacity to experience depression, and some still remain skeptical. Dr. Jules Bemporad, a psychiatrist at Harvard Medical School, says, ''Real depression comes from attributing external events to oneself, but children can only look at life intuitively and do not search for reasons.'' Nevertheless, advances in the diagnosis and treatment of adult depression have generated research on the applicability of those advances to children. Scientists estimate that 5 to 20 percent of all adults are depressed. Their inability to pinpoint its incidence more accurately suggests that they are using different definitions of depression. They do agree, however, that depressed adults feel sad and worthless, and are hopeless about the future. Depressed adults also commonly experience loss of interest in pleasurable activities, a lack of energy and disturbances in their sleep.

Eight major international banks have agreed to establish a new $70 million credit to Jamaica's recently elected centrist Government, and to refinance another $103 million in loans owed by the country, it was disclosed yesterday. The agreement, which was reached last Friday, must be approved by 100 banks around the world that have loans outstanding to the Caribbean nation. The eight major banks, led by Citibank, represent a large portion of the $103 million in current Jamaican loans outstanding to foreign banks.

President Reagan was treated for a partly collapsed lung today, but the bullet that entered his left side and lodged in the tissue of his left lung did not do much further damage, according to doctors who operated on him. Surgeons removed a .22-caliber bullet from the President's lower left lung. Neither Mr. Reagan's heart nor such vital blood vessels as the aorta were affected, Dr. Dennis S. O'Leary, dean for clinical affairs at George Washington University, said at a briefing this evening. ''The bullet was never close to any vital structure,'' he said. He called Mr. Reagan's prognosis ''excellent.''

An article on Sunday in The Times's New Jersey Weekly incorrectly reported the circumstances under which Thomas Michalak accepted a position as music director of the Kansas City Philharmonic in Missouri. Mr. Michalak will continue as conductor of the New Jersey Symphony. His contract with the Missouri orchestra takes effect Wednesday and calls for him to be music adviser for the 1981-82 season and to serve an unspecified term as principal guest conductor.

The Chicago Board of Trade, the nation's largest futures exchange, and a market that it created - the Chicago Board Options Exchange, the country's biggest options exchange -have become embroiled in a struggle over the trading of options on commodities and Government securities. So-called Ginnie Mae options are at the heart of the battle, which is similar to the current wrangle between the Securities and Exchange Commission and the Commodity Futures Trading Commission about which agency should have jurisdiction over the commodity options. Ginnie Mae options are options on mortgage futures contracts guaranteed by the Government National Mortgage Association. Members of the Board of Trade, angered by an S.E.C. decision allowing the options exchange to create a market in Ginnie Mae options, are complaining that the eight-year-old offspring of their organization is moving in on its territory and circumventing the country's securities laws. Millions of Dollars at Stake Ultimately, what is at stake is the potential to earn millions of dollars in commissions and trading profits.

Mayor Koch is expected to announce tighter water restrictions today, including a requirement that businesses and industry reduce consumption even more than they have since a ''drought emergency'' was declared two months ago. After an unusually dry March and with upstate reservoirs still below normal levels, Mr. Koch decided to move into the second phase of a three-stage program that would gradually impose stiffer controls on the way New Yorkers use water. The Mayor had been advised by environmental officials to move cautiously and perhaps not to resort to all the options available to him in the new phase of the emergency situation that has been in effect since last Jan. 19.

BEFORE World War II, riding an elevator usually involved delays, discomfort and anxiety caused by a balky and often jerky ride that ended with the car stopping several inches above or below the designated floor. Even today in some buildings with older elevators, service can be inefficient, inspiring such comments as: ''Why are all the elevators going up when I want to go down?'' or ''They should post an elevator schedule!'' But the elevators of the future should be very different. They will even be, in a mechanical sort of way, more compassionate, catering to people who are now afraid of traveling between floors. Engineers at the Westinghouse Elevator Company and the Otis Elevator Company, which together account for half the elevator sales in the nation, are reluctant to talk about their plans. But they acknowledge that their researchers are working on a variety of computerized devices that they feel will make an elevator ride more esthetically pleasing, more comfortable and less frightening.

Shooting of the President The President was shot in the chest by a gunman, apparently acting alone, as Mr. Reagan walked to his limousine after addressing a labor meeting at the Washington Hilton Hotel. James S. Brady, the White House press secretary, and two law-enforcement officers were also wounded by a series of shots. The President was reported in ''good'' and ''stable'' condition after undergoing two hours of surgery at George Washington University Hospital. (Page A1, Column 6.) Mr. Reagan's prognosis is ''excellent,'' a top hospital official said last night, adding that the President ''is alert and should be able to make decisions by tomorrow.'' Earlier, doctors removed a .22 caliber bullet from the President's partly-collapsed left lung, but said that the bullet did not do much further damage and that neither Mr. Reagan's heart nor vital blood vessels were affected. The emergency surgical procedures found no bleeding or damage in the abdominal area, and the President's vital signs were stable throughout his ordeal. (A1:6.)

President Reagan was shot in the chest today by a gunman, apparently acting alone, as Mr. Reagan walked to his limousine after addressing a labor meeting at the Washington Hilton Hotel. The White House press secretary and two law-enforcement officers were also wounded by a burst of shots. The President was reported in ''good'' and ''stable'' condition tonight at George Washington University Hospital after undergoing two hours of surgery. ''The prognosis is excellent,'' said Dr. Dennis S. O'Leary, dean of clinical affairs at the university. ''He is alert and should be able to make decisions by tomorrow.'' The hospital spokesman said surgeons removed a .22-caliber bullet that struck Mr. Reagan's seventh rib, penetrating the left lung three inches and collapsing it.

''All of us who care about this country and who care about our fellow citizens bear an important responsibility in whatever way we possibly can to rid this society and to rid this country of the kind of violence and hatred that we have seen.

The business community reacted with shock and uncertainty and financial markets halted trading abruptly as word spread yesterday afternoon that the President had been shot. Securities prices dropped sharply in the hectic 45 minutes between the first report that shots were fired at the President and the decision to stop trading on the New York Stock Exchange at 3:17 P.M. Across the nation, the normal conduct of business came to a nearstandstill. Workers and top executives alike gathered at television sets and radios to hear each news report of the President's condition. ''If Reagan is badly hurt, the effect in the markets could be severe because he is the symbol of the new economics,'' said James M. Davin, a managing director of the First Boston Corporation. ''But if he's up and around in a few days, it could be very bullish for the markets as the country and Congress rallies around its wounded leader.''