Ethanol induces conditioned social preference in male mice

Abstract

Background: Affiliative social interactions promote alcohol consumption, and alcohol also promotes affiliative behavior. Furthermore, for most species, moderate doses of ethanol (EtOH) and social affiliation are each rewarding. However, animal studies of drug and EtOH reward typically test individuals in isolation. To address social dimensions of EtOH reward, this study tested EtOH-induced conditioned social preference in male C57BL/6 mice with (ORCHX+T) and without (ORCHX) testosterone.

Methods: ORCHX+T males received EtOH (0, 1, 2, or 3 g/kg) intraperitoneally and were paired 4× for 30 minutes each with 1 of 2 stimulus males: with the CS- stimulus male after saline injection and with the CS+ male following EtOH. After pairing, time spent with CS+ and CS- males was measured in a 10-minute test.

Results: ORCHX+T test males showed conditioned preference for the CS+ male in response to 3 g/kg EtOH (change in preference: +71.3 ± 30.0 s/10 min, p < 0.05), but not for 0, 1, or 2 g/kg. By contrast, ORCHX males did not demonstrate conditioned preference for 3 g/kg EtOH (+16.0 ± 24.3 s/10 min, p > 0.05). In separate groups of mice, stimulus males (IS+) received EtOH during pairing to determine whether test mice prefer another intoxicated mouse. Both ORCHX+T and ORCHX test mice showed an increase in preference score for the IS+ mouse (ORCHX+T: +68.1 ± 24.0 seconds; ORCHX: +58.9 ± 19.6 seconds, p < 0.05).

Conclusions: These data demonstrate that EtOH promotes social preference in male mice, as it does in females. Testosterone enhances this effect.

Keywords: Alcoholic Intoxication; Association Learning; Conditioning, Classical; Social Behavior; Testosterone.

Figure 1

Experimental design. A: Testing conditioned social preference (CSP) for a stimulus male mouse (CS+) paired with ethanol vs another stimulus male (CS−) paired with saline. See Methods for details. B: In separate groups of mice (IS+ vs CS−), the conditioned stimulus male (IS+) also receives ethanol before pairing. C: Summary of pairings (CS+ or IS+) in gonadectomized male mice with (ORCHX+T) or without (ORCHX) testosterone replacement across the three experiments.

Figure 2

A: Preference score (mean±SEM) for the CS+ stimulus male mouse paired with 0, 1, 2 or 3 g/kg ethanol vs the CS− stimulus male during pre-test (open bars) and conditioned social preference (CSP, closed bars) in castrated male mice with testosterone replacement (ORCHX+T; n=7–10 each). B: Total interaction (seconds/10 min) with both stimulus males during pre-test and ethanol-induced CSP. Asterisks indicate significant difference by paired t-test vs pre-test values at the same ethanol dose.

Figure 3

A: Preference score (mean±SEM) for the conditioned stimulus male mouse (CS+ or IS+) paired with 3 g/kg ethanol vs the CS− stimulus male during pre-test (open bars), conditioned social preference (CSP, closed bars), and generalization (gray bars) in gonadectomized male mice with (ORCHX+T) or without (ORCHX) testosterone replacement (n=10–11 each). B: Total interaction (seconds/10 min) with both stimulus male mice during pre-test, ethanol-induced CSP and generalization tests. Asterisks indicate significant difference by Dunnett's test vs pre-test values in the same experimental group.

Figure 4

A: Preference score (mean±SEM) for the CS+ stimulus male mouse paired with 3 g/kg ethanol vs the CS− stimulus male during pre-test (open bars), conditioned social preference (CSP, closed bars), and generalization (gray bars) in castrated (ORCHX) male mice (n=10). CS+ and CS− stimulus males were castrates with testosterone replacement (ORCHX+T). B: Total interaction (seconds/10 min) with both stimulus male mice during pre-test, ethanol-induced CSP and generalization tests. Asterisk indicates significant difference by Dunnett's test vs pre-test values.

Figure 5

A: Olfactory investigation in seconds by a representative castrated (ORCHX) male mouse in response to repeated exposure to water and urine from 2 unfamiliar males (urine A and urine B). Urine was collected from castrates with (ORCHX+T, closed symbols) and without (ORCHX, open symbols) testosterone replacement. B: Change in investigation time (mean±SEM) during habituation and dishabituation (n=10). Asterisks indicate significant effects of urine order and source by RM-ANOVA.