Drinking mothers - perpetually jet-lagged offspring

Prenatal alcohol exposure can alter circadian rhythms in offspring

Children with fetal alcohol spectrum disorders (FASD) suffer from a variety of behavioral alterations. For example, they may exhibit alterations in sleeping and eating patterns, which may indicate that their circadian systems which control biological rhythms have been affected by alcohol exposure during development. A rodent study in the May issue of Alcoholism: Clinical & Experimental Research confirms that alcohol exposure during a period equivalent to the third human trimester influences the ability to synchronize circadian rhythms to light cues.

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For this study, researchers exposed male Sprague-Dawley rats to 6.0 g/kg of alcohol per day (n = 8), using an artificial rearing procedure, from postnatal days four through nine. The alcohol level represented heavy binge drinking. An artificially reared control group (n = 8) and a normally reared control group (n = 8) were also included in the study design. At 10 to 12 weeks of age, wheel-running behavior was continuously measured for eight days under a 12-hour light/12-hour dark (LD) cycle. Then the cycle was delayed by six hours and the rats were exposed to a new LD cycle for an additional six days. Their adjustment to the new cycle was evaluated.

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"This is the equivalent to a person undergoing exposure to 'jet lag,'" noted Earnest. "Basically, if you take a human and go across a number of time zones from east to west, similar to the light/dark cycle of these animals, some people will shift quickly, and some will not, and may even experience some physical problems or illness because of effects on their immune system. The responses of the alcohol-treated animals indicated that they resynchronized to the shifted light/dark cycle more slowly than the control animals."

The implications of these results for humans, added Earnest, are much broader than the term "jet lag" might indicate. "These individuals are going to have difficulties, in terms of their ability to function, while traveling across time zones and also during shift work," he said. "There are a couple of prominent examples in history regarding this: the Exxon Valdez and Chernobyl. The captain of the Exxon Valdez was not only working shift work, but he was drinking too, and unable to maintain a normal, necessary performance. With Chernobyl, the shift-work schedules were inappropriate and, at the time that the accident happened, poor mental and physical performances contributed to the disaster."

The underlying message, said Thomas, is that drinking alcohol during pregnancy can have long-lasting damaging effects to the offspring. "There is currently no known safe amount of alcohol that can be consumed during pregnancy, so it is best to abstain from alcohol drinking during pregnancy. We need to better understand the mechanisms of this dysfunction to determine if there are ways to mitigate the circadian dysfunction and behavioral dysregulation associated with developmental alcohol exposure."