Alcohol can have a deep impact on sexuality. Many people drink to "loosen up" a bit. Alcohol removes inhibitions, easing the inter-personal contact and giving people more (sometimes significantly more) guts to do what they desire, also being less aware of consequences.
Harvard researchers showed that frequent bingers engaged in unplanned sexual activity in 41 % of the cases, compared to 8 % in non binge drinkers and they had unprotected sex in 22 % of the cases compared to 4 %.
Now, a team at Penn State reveals, in a research published on the journal "PLoS ONE", for the first time, a physiological basis of how chronic alcohol consumption impacts male sexual behavior, like higher sex drive and lowered sexual inhibition. The study was made on fruit flies.
"Physiological evidence supporting various theories about the effect of alcoholic drinks has been lacking, so our now having a suitable animal model makes it possible to conduct much-needed laboratory research on this issue", said lead researcher Kyung-An Han, associate professor of biology and a neuroscientist at Penn State.
Previous researches investigated short-term effects of alcohol in flies, but the new approach was made by
delivering a daily dose of alcohol more similar to drinking habits of alcoholics and chronic alcohol abusers. It appears that male fruit flies, which normally court females, also actively court males when consume a daily dose of alcohol (ethanol).
"We identified three molecules that are crucial for 'ethanol-induced courtship disinhibition'," Han said.
The team experimented on engineered flies whose brain neurotransmitter dopamine could be inactivated temporarily by temperature values of 32o C.
"Without a temperature change, the transgenic males showed conspicuous inter-male courtship under the influence of ethanol; however, they exhibited negligible inter-male courtship when we changed the temperature to block the transmission of dopamine neurons in the brain. This result suggests that dopamine is a key mediator of ethanol-induced inter-male courtship", said Han.
Alcohol exposure also boosted, in male flies, inter-male courtship ("behavioral sensitization").
"If a behavior like alcohol consumption becomes more pleasurable the more often you do it, you are more likely to keep doing it", said Han.
Behavioral sensitization could be determined by adaptive changes in the neurons and molecules, provoked by chronic alcohol consumption, and it may be a model for future physiological investigation of alcohol addiction and connected behaviors.
"This part of our study demonstrates that sexual behavior is not determined only during an organism's development, but it also can be influenced by a post-developmental environmental factor; in this case, recurring exposure to ethanol", said Han.
The daily alcohol consume also caused chronic tolerance to its sedative effect in flies, like in other species too. The team also found that the alcohol provoked intermale courtship is impacted by aging.
"As flies get older, their cognitive capacities decline, making them more susceptible to the negative effect of ethanol on cognition", said Han.
Alcoholic middle-aged and old male flies (2- to 4-weeks old) were significantly more prone to the homosexual behavior than fully mature male flies (4-days old). All these results could be used for investigating the impact of alcohol consumption on sexual behavior in mammals, humans included.
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