Julius Axelrod, a pharmacologist and neuroscientist who shared the 1970 Nobel Prize in medicine for his insights into how human brain cells communicate with each other, died last December 29 at the age of 92. Axelrod's findings about the behavior of neurotransmitters -- the chemical messengers of the brain -- drew a clear connection between the physiology of the brain and emotional moods. His discoveries paved the way for the multibillion-dollar ­antidepressant drug industry, and in so doing helped give rise to what was later called by some "Prozac Nation."

Axelrod, who was known as ­"Julie," focused on how the neurotransmitters secreted by a brain cell travel across a synapse (the space between nerves) and are then picked up by a receptor on the surface of another cell. Before Axelrod's research in the late 1950s, scientists believed that neurotransmitters were broken down by enzymes in the brain after they crossed a synapse. But Axelrod's findings suggested that, instead, they were retrieved by the very cells that released them, in a process called "reuptake."