Chemical clues to alcohol intoxication.

Chemical clues to alcohol intoxication

The effects of alcohol intoxication on the activities of individual brain cells are not clear. Scientists are only beginning to work out the mechanisms of intoxication at a cellular and biochemical level (SN: 6/8/85, p. 357). An intriguing finding just reported may provide insight into alcohol's behavioral consequences.

Intoxicating doses of alcohol markedly affect the responses of certain brain cells to two natural chemicals, acetaylcholine and somatostatin-14. These substances, called neurotransmitters, carry signals between brain cells. The cells' responses to several other neurotransmitters -- glutamate, gamma-aminobutyric acid (GABA), norepinephrine and serotonin -- appear not to be significantly altered by alcohol intoxication, although the data for the last two substances are preliminary.

Jorge R. Mancillas, George R. Siggins and Floyd E. Bloom of the Scripps Clinic in La Jolla, Calf., first measured the electrical activity of several brain cells in each of 47 anesthetized rats. The cells are located in the hippocampus, a structure deep within the brain that plays an important role in learning and memory consolidation. After giving the rats alcohol doses equivalent to about four shots of bourbon for a man, the researchers injected a neurotransmitter into the brain area to see if the cells' electrical activity changed.

Acetylcholine prompts increases in cell activity, whereas somatostatin-14 causes a large drop in cell activity. These effects were enhanced in the alcohol-intoxicated rats, report the researchers in the Jan. 10 SCIENCE. Peak changes occurred 15 to 20 minutes after alcohol injections, and cell response returned to normal within 1 to 2 hours.

The effects of acetylcholine and somatostatin-14 appear to be closely linked. In an as yet unpublished study, the investigators find that somatostatin-14 naturally elevates responses to acetylcholine in the hippocampus. It is possible, they say, that alcohol enhances the effects of naturally occurring somatostatin in the hippocampus, which then "turns up" the responses of other cells to acetylcholine.

Although no similar effect was observed for GABA in alcohol-injected rats, J.N. Nestoros of McGill University in Montreal previously found that alcohol enhances the action of GABA in anesthetized cat brains (SN: 8/16/80, p. 102).

"It's a leap of faith to say our data is clinically relevant at this point," says Siggins, "but if the hippocampus is changed [during alcohol intoxication], it could explain lapses in memory and blackouts in some drinkers."