George K. Aghajanian (April 14, 1932 – July 4, 2023) was an American psychiatrist who was Emeritus Foundations Fund Professor at the Yale School of Medicine,[1] New Haven, Connecticut, in the Department of Psychiatry.

[2] George Aghajanian was of Armenian descent and was born on April 14, 1932, in Beirut, Lebanon.

Aghajanian was a medical officer in the United States Army in the starting days of his career.

[4] Aghajanian investigated the actions of LSD by which it produces hallucinations in the brain,[5] and uncovered the therapeutic mechanism of atypical antipsychotic drugs.

[6] He also found that application of serotonin (5-HT)[7] produces an increase in the frequency and amplitude of spontaneous excitatory postsynaptic potentials in layer V pyramidal cells of the neocortex and transitional cortex by whole-cell recording in rat brain slices.