Cue-alcohol associative learning in female rats

Abstract

The ability of environmental cues to trigger alcohol-seeking behaviors is believed to facilitate problematic alcohol use. We previously showed that the development of this cue-evoked alcohol approach reflects cue-alcohol learning and memory in the adult male rat; however, we do not know whether the same is true for similarly aged female rats. Consequently, adult Long-Evans female rats were allowed to drink unsweetened alcohol in the home cage (Monday, Wednesday, Friday; 24-h two-bottle choice; 5 weeks) and were subsequently split into two experimental groups: Paired and Unpaired. Groups were matched for ingested doses and alcohol bottle preference across the pre-conditioning home cage period. Both groups were trained in conditioning chambers using a Pavlovian procedure. For the Paired group, the chamber houselight was illuminated to signal access to an alcohol sipper. Houselight onset was yoked for the Unpaired group, but access to the alcohol sipper was scheduled to occur only during the intervening periods (in the absence of light). We found that in the Paired, but not Unpaired group, an alcohol approach reaction was conditioned to houselight illumination, and the level of cue-conditioned reactivity predicted drinking behavior within trials. Groups experienced equivalently low but non-negligible blood alcohol concentrations over the course of conditioning sessions. We conclude that cue-triggered alcohol-seeking behavior in adult female rats reflects associative learning about the relationship between alcohol availability and houselight illumination.

Keywords: Cue reactivity; Female rat; Low dose; Oral alcohol; Pavlovian conditioning.

Figure 1.. Equivalent ethanol exposure across cue conditioning.

A: Ingested dose (g/kg) per session shown across conditioning sessions in all the animals. Horizontal line shows a priori inclusion criterion (dose ≥0.30 g/kg/session across sessions 10-12). B: Relationship between blood ethanol concentrations detected approximately 10 min after the 8^th 10-s drinking opportunity in a conditioning session and total ingested ethanol doses in the same session for adult, female Long-Evans rats. Black and white triangles represent group Paired (n=10) and Unpaired (n=7), respectively. Regression line and 95% confidence limits shown by solid line and shaded area, respectively. C: Mean ± sem estimated blood ethanol concentrations across conditioning sessions (approximately 10 min after the 8^th drinking opportunity in the session) using ingested doses from A and regression equation from B for the same 17 rats.

Figure 2.. Conditioning of houselight-elicited anticipatory seeking.

Mean±sem level of sipper site approach (A) and faceplate contacts (B) paneled by trial phase (preCS bin: 5 s bin before houselight onset; CS bins 1-2: 1^st and 2^nd 5 s bin of illumination) shown across conditioning sessions (8 trials/session, 1 session/day, 12 consecutive days) for adult, female Long-Evans rats. Black and white triangles represent group Paired (n=10) and Unpaired (n=7), respectively. Approach data (maximum response level was 4) were derived from offline manual videoscoring (see main text Methods: Behavior Measurement for videoscoring details). Contact data were collected online using a modified lickometer (see main text Methods: Behavior Measurement for details).

Figure 3.. Within-session dynamics of houselight-elicited anticipatory seeking.

Mean ± sem level of anticipatory sipper site approach (A) and faceplate contacts (B) in the 5 s before light onset (bin −1) and over the 10 s post-light onset but pre-sipper onset (CS bin 1 and 2, each 5 s) paneled by trial (1-8) within conditioning session 12 for adult, female Long-Evans rats. Black and white triangles represent group Paired (n=10) and Unpaired (n=7), respectively. Approach data (maximum response level was 4) were derived from offline manual videoscoring.

Figure 4.. Equivalent drinking behavior across cue conditioning.

Mean±sem (A) latency (s) to start licking per trial and (B) number of licks per trial shown across conditioning sessions (8 trials/session, 1 session/day, 12 consecutive days) for adult, female Long-Evans rats. Black and white triangles represent group Paired (n=10) and Unpaired (n=6 out of 7 due to equipment malfunction), respectively.

Figure 5.. Conditioned cue reactivity predicts drinking latency, drinking intensity, and ingested dose in group Paired.

Relationships of latency to start licking per trial (A), total licks per trial (B), and ingested dose per session (C) to houselight-elicited sipper site approach level per trial (maximum = 4) on average across conditioning sessions 10-12. Data were from 10 adult, female Long-Evans rats. Solid lines in each panel represent the regression line. Dashed lines represent the upper and lower 95% confidence limits around the regression line.