High ethanol preferring rats fail to show dependence following short- or long-term ethanol exposure

The high ethanol preferring (HEP) rat shows high total ethanol consumption, high spontaneous activity and high consumption of novel tastants. Because these animals consume large quantities of ethanol daily, we sought to determine whether they could become alcohol-dependent by repeated exposures of varying lengths and withdrawals of alcohol, both in short- and long-term ethanol exposure.

Male and female HEP rats were subjected to short (14 days) or long (20 weeks) exposure to 10% ethanol in a two choice (vs. water) test. During the short- and long-term ethanol exposures, the animals were repeatedly deprived of ethanol for 5 days followed by reinstatement of the two-choice test. Moreover, pharmacological interventions (morphine and naltrexone), adulteration of ethanol by quinine and addition of saccharine to water were applied to test the lability of a possible alcohol deprivation effect.

In every case, deprivation produced a high initial intake of ethanol that lasted 0.5 h, but thereafter no significant increase in alcohol consumption, compared to predeprivation. Even after several months of continuous drinking of large amounts of ethanol, the animals were sensitive to adulteration of the alcohol solution by quinine, that reduced the intake, and still preferred a saccharine solution when presented as a free choice with the alcohol solution. Pretreatment with morphine increased ethanol consumption in the first 0.5 h following deprivation, whereas naltrexone reduced it.

Taste reinforcement is probably a major component of alcohol drinking by the HEP rats, and that while these rats consume large quantities of ethanol both in the short- and long-term, they do not show a robust alcohol deprivation effect.