Mounting evidence suggests that parental ingestion of abused drugs influences the physiology and behavior of future generations in the absence of prenatal exposure (Vassoler et al, 2013a). However, few studies have examined potential mechanisms of transmission of addiction-related phenotypes. Therefore, we developed a rat model to delineate a heritable phenotype resulting from the self-administration of cocaine. Our research indicates that the sons of cocaine-experienced male rats find cocaine-less reinforcing, leading them to consume considerably less cocaine than controls (Vassoler et al, 2013b). Increased levels of cortical brain-derived neurotrophic factor (BDNF) may be the underlying cause of the cocaine resistance observed in the sons. These findings show that cocaine-induced changes in physiology can be inherited by sons from their fathers. The reason for the sex specificity is unclear, but may be due to intergenerational effects on gene transcription interacting with subsequent hormonal influences.

We usually think about inherited changes in physiology occurring via natural selection on an evolutionary timescale. However, a growing body of evidence indicates that environmental information can be transmitted from one generation to the next. For example, epidemiological data show that a fetus exposed to famine early in pregnancy will tend to be born small but will be more prone to obesity, diabetes, and mental health issues as an adult (Lumey et al, 2011). Some of these health problems also plague the grandchildren of mothers malnourished in early pregnancy (Lumey et al, 2011). The latter is a potential example of epigenetic inheritance, defined as changes in phenotype caused by mechanisms other than alterations in DNA sequence.

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