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I Synthesize, Therefore I Think

Dateline: 01/19/98

By Alan Bruzel

Background:

Chemicals mediate the way you think, act, and feel. Those naturally occurring in the brain range in size from tiny iron ions and simple carbon monoxide molecules to gigantic proteinaceous tangles found around nerve fibers in Alzheimer's disease. (Not to be confused with the "tangles of Neæra's hair" found in Milton's "Lycidas," line 69.)

But iron, carbon monoxide, and the amyloid peptides of Alzheimer's disease are relative newcomers to the brain chemical roster. Let us turn then to two old war-horses of the neurochemistry laboratory: dopamine and serotonin.

Dopamine:

The pleasure derived from addictive drugs results from elevated dopamine levels. Heroin and amphetamine stimulate the brain's production of dopamine. (Result: a high level of dopamine.) Cocaine prevents dopamine's degradation. (Same result: a high level of dopamine.) Tobacco both stimulates dopamine's production (via nicotine) and prevents dopamine's breakdown (by processes as yet unclear). Positron emission tomography (PET) brain scans demonstrate smokers keep their pleasure-giving dopamine longer in their brains than do non-smokers.

By stimulating the production of dopamine AND preventing its breakdown, smokers have their cake and eat it, too. Tobacco thus shares the addictive properties of two of the world's most illegal drugs. Rudyard Kipling has his pharmacological facts straight when he asserts: "And a woman is only a woman, but a good Cigar is a Smoke." He more specifically names names: "The wee little whimpering Love and the great god Nick o' Teen." (Both quoted from his paean to cigars, "The Betrothed.")

Mentioning PET, which requires the positron-emitting property of such isotopes as carbon-11 and fluorine-18, leads me to sketch the story entitled "The Return of ¹¹C" or "Bis dat qui cito dat" (he gives twice who gives quickly).

¹¹C began its life in the 1930's as the first radioactive carbon isotope used in research. Alas, glory is short-lived. ¹¹C was replaced in the 1940's by ¹⁴C, an electron-emitter. ¹⁴C's claim to fame was its longer half-life: 5,570 years versus 20.5 minutes for ¹¹C. ¹⁴C thus proved a boon to researchers who dawdled over their lunches. Today, ¹⁴C still carries the field, but thanks to PET's diagnostic wizardry, ¹¹C once again holds its head up high.

Yes, ¹¹C's fortunes have changed, but its half-life has not. For best results, work quickly (preferably next door to a cyclotron).

Serotonin:

Serotonin, like dopamine, is another neurotransmitter produced by the brain. Its concentration rises following meals containing sugars and starches. Dieters avoiding carbohydrates maintain an elevated serotonin level by taking the diet drugs fenfluramine and dexfenfluramine. And why should I keep my serotonin level high? Because both violent behavior and PMS are attributed to low serotonin levels.

Other issues:

Finally, there are those convinced that changes in brain chemistry stem from playing certain games or from eating chocolate.

And others are capitalizing on the public attention surrounding brain chemicals by offering blue green algae (touted to enhance neuropeptide levels) and even the neuropeptides, themselves. (Why not simply eat your next door neighbor's brain? Social niceties aside, the disease kuru is linked to human brain ingestion.)

Hopefully, I've provided some food for thought. In any event, here are more brain chemistry sites worth the visiting:

Howard Hughes Medical Institute
Generous collection of articles exploring the senses of smell, hearing, and vision.

Society for Neuroscience
Professional society of scientists and physicians.

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