Voluntary co-consumption of alcohol and nicotine: Effects of abstinence, intermittency, and withdrawal in mice

Abstract

Alcohol and nicotine are often used together, and there is a high rate of co-occurrence between alcohol and nicotine addiction. Most animal models studying alcohol and nicotine interactions have utilized passive drug administration, which may not be relevant to human co-addiction. In addition, the interactions between alcohol and nicotine in female animals have been understudied, as most studies have used male animals. To address these issues, we developed models of alcohol and nicotine co-consumption in male and female mice that utilized voluntary, oral consumption of unsweetened alcohol, nicotine and water. We first examined drug consumption and preference in single-drug, sequential alcohol and nicotine consumption tests in male and female C57BL/6 and DBA/2J mice. We then tested chronic continuous and intermittent access alcohol and nicotine co-consumption procedures. We found that male and female C57BL/6 mice readily co-consumed unsweetened alcohol and nicotine. In our continuous co-consumption procedures, we found that varying the available nicotine concentration during an alcohol abstinence period affected compensatory nicotine consumption during alcohol abstinence, and affected rebound alcohol consumption when alcohol was re-introduced. Consumption of alcohol and nicotine in an intermittent co-consumption procedure produced higher alcohol consumption levels, but not nicotine consumption levels, compared with the continuous co-consumption procedures. Finally, we found that intermittent alcohol and nicotine co-consumption resulted in physical dependence. Our data show that these voluntary co-consumption procedures can be easily performed in mice and can be used to study behavioral interactions between alcohol and nicotine consumption, which may better model human alcohol and nicotine co-addiction.

Keywords: Abstinence; Alcohol; Consumption; Intermittent; Nicotine; Withdrawal.

Figure 1

Experiment 1: Alcohol and nicotine consumption and preference in sequential alcohol and nicotine two-bottle choice tests in male and female C57BL/6 and DBA/2J mice. A) Female C57BL/6 mice consume more alcohol compared with male C57BL/6 mice at the 10 and 14% alcohol concentrations. Male DBA/2J mice consume more alcohol at the 6 and 20% concentrations compared with female DBA/2J mice. B) Male DBA/2J mice have higher alcohol preference compared with female DBA/2J mice at the 6% alcohol concentration. C) Female C57BL/6 mice have higher average daily nicotine consumption at the 40 and 50 µg/mL concentrations, D) and have higher nicotine preference at the 50 µg/mL concentration compared with male C57BL/6 mice. *P<0.05, **P<0.01, ****P<0.0001 compared between sexes within a strain using Sidak’s multiple comparison post-hoc test. Male C57BL/6 n=10, female C57BL/6 n=10, male DBA/2J n=10, female DBA/2J n=10.

Figure 2

Experiment 2A: Alcohol and nicotine co-consumption in a continuous access 3-bottle choice test in male and female C57BL/6 mice. The average daily alcohol and nicotine consumption levels in A) male and C) female mice. Alcohol, nicotine and water preference for B) male and D) female mice. The nicotine concentration was maintained at 30 µg/mL during the alcohol abstinence week. Average daily nicotine consumption and preference increased during the alcohol abstinence week in both males and females. **P<0.01, ****P<0.0001 for an overall effect of week in a two-way repeated measures ANOVA. Male C57BL/6 n=15, female C57BL/6 n=15.

Figure 3

Experiment 2B: Alcohol and nicotine co-consumption in a continuous access 3-bottle choice test in male and female C57BL/6 mice. The average daily alcohol and nicotine consumption levels in A) male and C) female mice. Alcohol, nicotine and water preference for B) male and D) female mice. The nicotine concentration was decreased to 20 µg/mL during the alcohol abstinence week. Average daily alcohol consumption increased when alcohol was re-introduced for both males and females. Nicotine consumption decreased during the week of alcohol abstinence in both sexes. *P<0.05, ***P<0.001, ****P<0.0001 for an overall effect of week in a two-way repeated measures ANOVA. Male C57BL/6 n=15, female C57BL/6 n=15.

Figure 4

A) In male C57BL/6 mice, the average daily alcohol consumption was lower for the 10 and 20% concentrations in the continuous access co-consumption 3-bottle choice tests compared with the sequential, continuous access 2-bottle choice tests. ****P<0.0001 using a Sidak’s multiple comparison post-hoc test. B) Female C57BL/6 mice showed similar levels of average daily alcohol consumption in both the 3-bottle choice test and the sequential 2-bottle choice test. There was no difference in the average daily consumption for the 30 µg/mL nicotine concentration between the 3-bottle choice test and the 2-bottle choice test for C) males or D) females. Continuous access 3-bottle choice test: male C57BL/6 n=28–30, female C57BL/6 n=29–30. Continuous access 2-bottle choice test: male C57BL/6 n=10, female C57BL/6 n=10.

Figure 5

Experiment 3: Alcohol and nicotine co-consumption in an intermittent 3-bottle choice test. During week 1, mice received 3% alcohol and 5 µg/mL nicotine on Monday, 6% alcohol and 10 µg/mL nicotine on Wednesday, and 10% alcohol and 15 µg/mL nicotine on Friday. During weeks 2–4, mice received 20% alcohol and 30 µg/mL nicotine every Monday, Wednesday and Friday. The average daily alcohol and nicotine consumption levels in A) male and C) female mice. Alcohol, nicotine and water preference for B) male and D) female mice. Male C57BL/6 n=15, female C57BL/6 n=15.

Figure 6

Withdrawal scores for male (n=15) and female (n=15) C57BL/6 mice after the intermittent alcohol and nicotine co-consumption test. *P<0.05, **P<0.01 in a one-sample, two-way Student’s t-test.

Figure 7

The average daily alcohol consumption for A) male and B) female mice during the intermittent access 3-bottle choice test (I) compared with the continuous access 3-bottle choice test (C). **P<0.01 using a Student’s t-test. The average daily nicotine consumption for the 30 µg/mL concentration in C) males or D) females between the continuous and intermittent access 3-bottle choice tests. Continuous access 3-bottle choice tests: male and female C57BL/6 n=28–30 each. Intermittent access 3-bottle choice test: male and female C57BL/6 n=15 each.