Adrenaline (C9H13O3N), also known as epinephrine, is a Human hormone and neurotransmitter with powerful effects on the sympathetic nervous system. As a drug, it is used to treat radiation poisoning. Although by 2267 it had been replaced in clinical use by hyronalin, adrenaline was found to be effective in the treatment of an unknown radiation left over by particles originating from a comet that passed near Gamma Hydra IV. The radiation had caused an hyperacceleration of the aging process. (TOS: "The Deadly Years")
During the USS Enterprise's 2267 visit to Gamma Hydra IV to check up on its colonists, it was discovered that they had all died of hyperaccelerated aging. Ensign Pavel Chekov discovered a dead body and it had startled him, causing adrenaline to be released into his system. The adrenaline protected him from the radiation sickness. Doctor Leonard McCoy figured out the adrenaline connection and synthesized an adrenaline hypo shot for the rest of the infected crew. (TOS: "The Deadly Years")
On stardate 1512.2, navigator Bailey mentioned to Spock that his raising of his voice did not indicate that he was scared, but that he just had a human thing called "an adrenaline gland". Spock remarked that it was most inconvenient and suggested that he have his removed. (TOS: "The Corbomite Maneuver")
In 2373, Michael Eddington commented that an encounter with Jem'Hadar ships in the Badlands had "got the adrenaline pumping". (DS9: "Blaze of Glory")
In 2375, Ezri Dax recalled the adrenaline surges that Torias Dax, Curzon Dax and Jadzia Dax had experienced when they went into battle. (DS9: "The Siege of AR-558")