Differential alcohol drinking behaviour and dependence in the Naples low- and high-excitability rat lines

Alcoholism is composed of a series of phenomena, which can be approached in model systems. Our aim was to investigate psychogenetics of alcohol drinking behaviour and dependence in the Naples rat lines. Thus, adult male rats of the Naples low- (NLE), high-excitability (NHE) and random-bred control (NRB) lines had 24-h access to a four-bottle system with tap water and 5, 10 and 20% alcohol solutions. Total voluntary alcohol intake and preference were measured during a 6-week period. In order to analyze behavioural dependence, two abstinence periods were introduced, followed by re-exposure to the bottles. The first was a pure re-test and the second was a quinine test (adding 0.02% quinine alcohol solution). Finally, to verify the role of opioids on alcohol drinking behaviour, rats received naltrexone (5 mg/kg i.p.). Thirty minutes later, they had access for 2 h to a three-bottle system with water, 5 and 20% alcohol solution, respectively. Results indicate that (i) total alcohol intake on day 1 was higher in both NLE/NHE, becoming higher in NLE rats during the 6-week period, (ii) different alcohol preference patterns in the Naples lines were observed over time of testing, (iii) during re-test, NLE rats showed neither reversibility nor alcohol deprivation effect, (iv) during quinine test, only NLE rats reduced alcohol intake to a lower extent and (v) naltrexone reduced by 50% the intake of the preferred solution. Therefore, the NLE rats appear as a new model for studying the neural substrates of the dependence behaviour.