MK ULTRA was one such program. They got “volunteers”, dosed them with LSD, and then interrogated them. As wel as lots of other shenanigans involving other drugs (Ken Kesey got his first LSD through MK ULTRA)
According to the book “In Search of the Manchurian Candidate” some of the people were not exactly volunteers. There were some Senate hearings held right after the main experimenter got rid of hundreds of pounds of files, just cleaning up, you know, after nearly 20 years of experiments.
According to the book, the CIA set up a brothel in San Fran with cameras and microphones and surveillance mirrors. They’d get a john off the street and dose him with something while he was with one of the girls.
There was a guy, Frank Olsen, who had worked Project NAOMI (using biologicals as covert political tools) for years and was having second thoughts, so the story goes. He wound up with MK ULTRA guys in a NYC hotel, where apparently they gave him a surprise dose (very common within CIA circles apparently) and he wound up jumping out the window.
They volunteered to get the kind of free drugs that were popular with people of that era. Also notice that they filed in San Francisco.