Figure 1

(a) Mean (±s.e.m.) change in time (s) spent in predator-paired context from pre-conditioning test to post-conditioning test, quantified as post-test score minus pre-test score. Rats (Experiment 1) were divided into Avoiders (n=23) and Non-Avoiders (n=14) based on avoidance of predator-paired chamber at 24 h post conditioning, and then were tested again for avoidance 6 weeks later. Rats that exhibited high avoidance of the predator-paired chamber at 24 h post-conditioning also exhibited avoidance 6 weeks later. (b) Scatter plot for individual rat (Experiment 3) shows change in preference for a context repeatedly paired with an appetitive stimulus (saccharin+glucose solution) versus change in preference for a context repeatedly paired with predator odor. There was no predictive value by the degree to which a rat conditioned the appetitive stimulus for the degree to which a rat conditioned the aversive stimulus. This also suggests that differences in avoidance are not attributable to differences in ability of rats to learn. (c) Scatter plot for individual rat (Experiment 3) shows percent time spent in open arms of EPM (5-min test) in experimentally naive rats (index of innate anxiety-like behavior) versus change in preference for a context repeatedly paired with predator odor. There was no predictive value by innate anxiety-like behavior for the degree to which a rat conditioned the aversive stimulus. (d) Mean operant alcohol responses (±s.e.m.) per 30 min session for Avoider, Non-Avoider and non-stressed control groups (Experiments 1 and 2 combined) across the last 3 days of the pre-conditioning baseline self-administration period. Groups did not differ in baseline alcohol self-administration. These data also provide further support for the notion that differences in avoidance are not attributable to differences in ability of rats to learn. (e) Mean (±s.e.m.) operant presses for alcohol per 30-min self-administration session by rats in Experiment 2 (results similar in Experiment 1, see text) during intermittent testing across the 19 days following exposure to predator odor (Avoider and Non-Avoider groups) or no odor (control group). Avoider rats exhibited persistent increases in operant alcohol responding relative to the two other groups and their own baseline across the 19 days following exposure to odor. *P<0.05 significant main effect of group. Avoiders exhibited marginally non-significant increases in alcohol responding relative to Non-Avoiders (P=0.06) and unstressed Controls (P=0.055). (f) Mean (±s.e.m.) self-administration of alcohol solution adulterated with progressively increasing quantities of quinine, quantified as percent change from baseline (10% w/v ethanol plus 0% quinine) for each rat (Experiment 1). A 10 × higher concentration (0.025% vs 0.0025%) of quinine was required to reduce operant alcohol self-administration in Avoider rats vs Non-Avoider and Control rats, indicative of more compulsive-like alcohol drinking in Avoider rats. **P<0.001 Avoiders responded significantly more for alcohol + 0.0025% quinine relative to unstressed Controls. There was a non-significant tendency of Avoiders to press more for this solution than Non-Avoiders (P=0.10). (g) Scatter plot for individual rat (Experiment 2) shows change in preference for predator-paired context versus percent change in operant alcohol responding at day 19 post-odor exposure relative to baseline. Rats that exhibited high avoidance of the predator-paired context 24 h post-odor exposure self-administered more alcohol at 19 days post-odor exposure.