“Alcohol is the king of liquids. It excites the taste to the highest degree, its various preparations have opened up to mankind new sources of enjoyment. It supplies to certain medicines an energy which they could not have without it.”
(Brillat-Savarin JA. Physiologie du Goût. Feydeau, Paris, 1826).
The word “alcohol,” according to Merriam-Webster’s dictionary, finds its roots in the Arabic al-kuhul (or kohl, cohol, or kohol) to mean a powder of antimony or galena used by women to darken the eyebrows. The name alcohol was derived through Medieval Latin from Arabic. Because of the fineness of this powder, it was later applied to highly rectified spirits, a signification unknown in Arabia. Alcohol generically represents a wide range of compounds (Figure 6.1), but the alcohol suitable for drinking is ethanol (or ethyl alcohol or ethanol; Box 6.1). Alcohol is found in all substances that contain glucose. It is the product of the “saccharine principle,” which is the term used in distillation for the conversion of any carbohydrate to glucose that can then be subjected to fermentation. Fermentation is the conversion of glucose and water in the presence of yeast to ethanol and carbon dioxide, and this is a common biological reaction in nature. Five agents are required for alcoholic fermentation: sugar (or starch to form glucose), water, heat, ferment (usually the yeast Saccharomyces cerevisiae), and air. Yeast converts glucose to alcohol up to a level of approximately 12%. Above this level, the alcohol becomes toxic to the yeast, which then dies. Such a process occurs in nature in seed germination and fruit ripening. Any source of glucose is sufficient to produce alcohol through the process of fermentation, and a wide range of glucose sources is used as the basis of numerous alcoholic beverages worldwide ( Table 6.1). To raise alcohol (ethanol) concentrations above 12%, the yeast-converted fermentation mixture must be distilled. The fermentation mixture is heated, and the ethanol vaporizes at a lower temperature than water. When cooled in some form of a condensation device (often a cool metal or glass container), the ethanol can again be captured as a liquid.
Figure 6.1 Chemical structures and registry numbers for various alcohols from the Chemical Abstracts database. Notice that each structure has a chain of four carbons or less. [Taken with permission from Koob GF, Le Moal M. Neurobiology of Addiction. Academic Press, London, 2006.]
SYNOPSIS OF THE NEUROPHARMACOLOGICAL TARGET FOR ALCOHOLAll alcoholic products contain ethyl alcohol (ethanol), which is the main psychoactive ingredient in alcoholic beverages. Alcohol does not bind as a direct agonist at receptors in the brain but rather appears to be sequestered in transmembrane water pockets and modulates receptors (termed ethanol-receptive elements) to produce its behavioral effects. Alcohol is considered a sedative-hypnotic, but it can also produce psychostimulant-like effects that are attributable to disinhibition. Alcohol-receptive elements have been hypothesized to be located on ion-gated receptors, such as γ-aminobutyric acid-A (GABAA), glycine, and glutamate receptors. The intoxicating effects of alcohol are mediated by the activation of multiple neurotransmitter systems (predominantly GABA, opioid peptides, and dopamine) in the origin areas (ventral tegmental area) and terminal areas (nucleus accumbens) of the mesocorticolimbic dopamine system and extended amygdala (central nucleus of the amygdala, bed nucleus of the stria terminalis, and a transition zone in the shell of the nucleus accumbens). The addiction potential of alcohol largely derives from powerful within-system neuroadaptations (signal transduction mechanisms) and between-system neuroadaptations (neurocircuitry changes) in the brain motivational and stress systems.
Common Alcoholic Beverages
For more information, visit http://en.wikipedia.org/wiki/Alcoholic_beverage#Types_of_alcoholic_beverages.