His death was announced by the University of Cambridge's Trinity College, where he served as master from 1984 to 1990, but no details were released.
Working with fellow Nobel laureate Sir Alan Hodgkin, Huxley solved a puzzle that had perplexed biologists for decades: how nerves generate the electrical impulses that control muscle activities and even thoughts. That work "did for the cell biology of neurons what the structure of DNA did for the rest of biology," 2000 Nobel laureate Eric R. Kandel later wrote.
Biologists had known since the 1771 experiments of Italian physicist Luigi Galvani that giving a frog leg an electrical shock would cause it to contract, suggesting that muscle activity was electrically regulated. But it was not clear how the tissues could generate such an electrical stimulus and how it could be transmitted through cells.
Huxley and Hodgkin approached the problem by studying a squid nerve cell known as the giant axon. The giant axon, which can be up to 1 millimeter (0.04 inches) in diameter, stretches the length of the squid's body to control ejection of water for propulsion, and nerve impulses travel especially rapidly through it.
By placing tiny electrodes in the axon at various locations, they were able to measure the electrical potential inside the nerve as it transmitted an electrical current. They concluded that the current was carried by electrically charged atoms called ions. When the current reaches each cell, it causes a channel known as a sodium gate to open, allowing sodium ions to flow into the cell.
Once enough sodium is in the cell, that triggers a second set of gates on the opposite end that allow potassium ions to escape. Those ions cause the process to repeat at the next cell.
The gates themselves could not be visualized with the technology available at the time, but Huxley, working on a very primitive computer, used the laws of physics to calculate the electrical potentials that should be obtained if their model was correct. The calculated values were very close to those that were observed, confirming their hypothesis. Only much later were the ion channels actually imaged.
Huxley and Hodgkin shared their Nobel with Sir John Eccles of Australia, who explained how signals were transmitted between cells. Both Britons were knighted for their work in 1974.
Huxley later worked to explain how muscle fibers contract. For that work, he devised and built a microtome to make very thin slices of tissue for study in the electron microscope and a micromanipulator.
Andrew Fielding Huxley was born Nov. 22, 1917, in London to a celebrated family. His grandfather was biologist Thomas Henry Huxley, an early supporter of Charles Darwin's theory of evolution. His father, Leonard, was a writer who, among other things, compiled a history of Thomas Huxley. Andrew's older half-brothers were the author Aldous Huxley and biologist Julian Sorel Huxley.
When Andrew was 12, his parents bought the mechanically minded boy and his brother David a lathe, which Andrew used to make wooden candlesticks and a functioning internal combustion engine. He later used the same lathe to manufacture many of the laboratory instruments he needed.
He received a scholarship to Trinity College, where he intended to become a physicist. But he needed another science course, and a friend recommended physiology — a suggestion that changed Huxley's life. He received a bachelor's degree in 1938 and a master's in 1941.
In 1939, he had started working with Hodgkin at the Plymouth Marine Biological Laboratory, but after a year their work was interrupted by the advent of World War II. He spent the war working to provide radar control for gunnery, first for antiaircraft guns and later for naval artillery. After the war, he returned to Plymouth. The research partners published their first finding in 1951 and a series of highly regarded papers in 1952.
Huxley spent all of his career at University College London and Trinity. He was elected to the Royal Society in 1955 and served as its president from 1980 to 1985 — a position also held by his grandfather Thomas. As Thomas did, he used his inaugural presidential address to stoutly defend the theory of evolution, although he conceded that the question of the creation of the universe was still open.
Huxley edited two journals and received many honors, including the presidency of the British Assn. for the Advancement of Science and the International Union of Physiological Sciences.
His wife of 55 years, the former Jocelyn Richenda Gammell Pease, died in 2002. Huxley is survived by five daughters and a son.