The effects of social instability stress and subsequent ethanol consumption in adolescence on brain and behavioural development in male rats.

Excessive drinking in adolescence continues to be a problem, and almost a quarter of young Canadians have reported drinking five or more in one occasion in recent surveys. The consequences of such drinking may be more pronounced when commenced in adolescence, given the ongoing brain development during this period of life. Here, we investigated the consequences of three weeks intermittent access to ethanol in mid-adolescence to early adulthood in rats and the extent to which a stress history moderated the negative consequences of ethanol access. In experiment 1, male rats that underwent adolescent social instability stress (SS; daily 1 hr isolation + return to unfamiliar cage partner every day from PND 30-45) did not differ from control (CTL) rats in intake of 10% ethanol sweetened with 0.1% saccharin (access period; PND 47-66). Ethanol drinking reduced proteins relevant for synaptic plasticity (αCaMKII, βCaMKII and PSD-95) in the dorsal hippocampus, and in CTL rats only in the prefrontal cortex (αCaMKII and PSD 95), attenuating the difference between CTL and SS rats in the water-drinking group. In experiment 2, ethanol also attenuated the difference between SS and CTL rats in a social interaction test by reducing social interaction in SS rats; CTL rats, however, had a higher intake of ethanol than did SS rats during the access period. Ethanol drinking reduced baseline and fear recall recovery concentrations of corticosterone relative to those exposed only to water, although there was no effect of either ethanol or stress history on fear conditioning. Ethanol drinking did not influence intake after 9 days of withdrawal, however, ethanol-naïve SS rats drank more than did CTL rats when given a 24-hour access in adulthood. These results reveal a complex relationship between stress history and ethanol intake in adolescence on outcomes in adulthood.