Genetic studies of alcohol dependence in the context of the addiction cycle
Alcohol dependence is heritable. Two factor contribute to alcohol dependence - environmental conditions, and genes. It is estimated that genes contribute to about 50-60% of the phenotype.It is hard to nail down the exact genes because everything is heterogenous. Researchers study twin studies and adoption data to define the genetic components of alcohol dependence. Both twin and adoption studies show high correlation between family members and the participants susception to alcohol dependency. Research then ran an GWAS (genome wide association study) and found multiple genetic variants that contribute to alcoholism.
The Evolution of Drosophila melanogaster as a Model for Alcohol Research
In this paper, researchers investigate the relationship between ethanol and Drosophila in an ecological and evolutionary perspective. Fruit flies have many adaptations due to a prevalence of ethanol in their environment. Typically fruit flies are found near ripe food which can hold up to 5% ethanol. Flies metabolize ethanol and use it as an energy source. Fruit flies also contain a smaller version of Alcohol Dehydrogenase (ADH) which differs slightly from the longer vertebrate version of the protein, indicating that fruit flies had an earlier ecological change to ethanol in ripe fruit. ADH is also necessary for survival on ethanol foods. Researchers found that having ethanol as the only source of calories induced a longer survival rate indicating that ethanol is a strong source of calories for Drosophila. Behavioral studies of Drosophila have shown that fruit flies with a longer and stronger exposure to ethanol ...
Ethanol Sensitivity and Tolerance in Long-Term Memory Mutants of Drosophila melanogaster - Berger - 2008 - Alcoholism: Clinical and Experimental Research - Wiley Online Library
Mutants of the learning and/or memory pathways have differential responses to ethanol tolerance. Some mutants increased amnesia/learning loss, while others had an opposite effect to ethanol tolerance. Researchers tested a collection of 60 long-term memory mutants for 52 loci where these mutants limit learning so normal function of each mutation are thought to play into the long-term memory pathway. Researchers then ran an ethanol assay and quantified the ethanol tolerance of each mutant. The data suggests that these pathways overlap and suggest specific genes for each pathway.
By generating starvation- resistant flies through experimental evolution, these researchers at UNLV were able to more closely observe the relationships between sleep behavior, feeding, foraging, and starvation resistance. Because sleep and feeding are related to metabolic rates, they could potentially contribute to Drosophila melanogaster resistance under starvation conditions. The flies used in this experiment have been bred over 60 generations in order to become starvation resistant. These flies were bred on an agar diet that was devoid of calories, and live around 18 days when under starvation conditions. Flies that have not been selected for starvation resistance survive around 2-3 days.
Qingying Menga, Yumei Zhuanga, Zhe Yinga, Rahul Agrawala, Xia Yanga, , , Fernando Gomez-Pinillaa,b, ,
Dopamine modulates acute responses to cocaine, nicotine and ethanol in Drosophila
In this paper researchers study the role of dopamine in different drug exposures. To test how flies responded to cocaine and nicotine they tested how quickly they could climb up a glass tube. With the effects of the drug, flies would remain at the bottom of the tube. Cocaine recovery time was fifteen minutes for moderate doses and nicotine was five minutes for moderate doses. To test the effects of Dopamine, researchers used Dopamine depleted flies by feeding them a competitive antagonist to tyrosine hydroxylase which in necessary for dopamine synthesis. A complete lack of Dopamine results in lethality, so flies tested only have significantly reduced dopamine in their systems. When these flies were tested with cocaine or nicotine they shows a 35% reduction in ability to geotax (climb). These factors are contributed to dopamine reductions, due to a normalized response when the dopamine reduction was rev ...
Survival of organisms depends partially on their response to stress. For Humans and other organisms, these responses are regulated, it part, by epinephrine and norepinephrine. This system in humans contains many feedback loops and is complicated to study. Invertebrate systems are easier to study. This research focuses on how similar chemicals in Drosophila have an effect certain characteristics. Specifically their research found that chemicals had an effect on lifespan, starvation resistance, and body fat in fruit flies, as well as other minor traits.
In this paper the author tested the effect of ethanol consumption on Drosphila's courtship patterns and fecundity rate. Virgin males are separated into two groups; one getting food with water and one made with ethanol. Food consumption was highly regulated for 4 days. After four days males were combined with virgin females. They observed a significantly shorter courtship period, but a significant higher fecundity rates for flies with ethanol exposures. Flies also prefered ethanol food significantly to water food.