Conditioned stimuli affect ethanol-seeking by female alcohol-preferring (P) rats: the role of repeated-deprivations, cue-pretreatment, and cue-temporal intervals

Abstract

Rationale: Evidence indicates that drug-paired stimuli can evoke drug-craving leading to drug-seeking and repeated relapse periods can influence drug-seeking behaviors.

Objectives: The present study examined (1) the effect of an interaction between repeated deprivation cycles and excitatory conditioning stimuli (CS+) on ethanol (EtOH)-seeking; (2) the effects of EtOH-paired cue-exposure in a non-drug-paired environment on subsequent conditioning in a drug-paired environment; and (3) the temporal effects of conditioned cues on subsequent EtOH-seeking.

Methods: Adult female alcohol-preferring (P) rats were exposed to three conditioned odor cues; CS+ associated with EtOH self-administration, CS- associated with the absence of EtOH (extinction training), and a neutral stimulus (CS⁰) presented in a neutral non-drug-paired environment. The rats underwent four deprivation cycles or were non-deprived, following extinction they were maintained in a home cage for an EtOH-free period, and then exposed to no cue, CS+, CS-, or CS⁰ to assess the effect of the conditioned cues on EtOH-seeking behavior.

Results: Repeated deprivations enhanced and prolonged the duration of CS+ effects on EtOH-seeking. Presentation of the CS- in a non-drug-paired environment blocked the ability of a CS+ to enhance EtOH-seeking in a drug-paired environment. Presentation of the CS+ or CS- in a non-drug-paired environment 2 or 4 h earlier significantly altered EtOH-seeking.

Conclusion: Results indicated an interaction between repeated deprivation cycles and CS+ resulted in a potentiation of CS+ evoked EtOH-seeking. In addition, a CS- may have therapeutic potential by providing prophylactic protection against relapse behavior in the presence of cues in the drug-using environment.

Keywords: Alcohol relapse; Alcohol-preferring (P) rats; Drug deprivation; Drug relapse; Drug-craving; Drug-seeking.

Figure 1:

Depicts the experimental timelines for the Non-Deprived and Repeated Deprivation.

Figure 2:

Depicts the experimental timelines for the Non-Deprived and Repeated Deprivation cycles with conditioned cues prior (pretreatment) to PSR EtOH-seeking and during PSR EtOH-seeking.

Figure 3:

Depicts the experimental timelines for temporal experiments with conditioned cues.

Figure 4:

Depicts the mean (± SEM) responses on the lever previously associated with the delivery of EtOH for the Repeated Deprivation (Rep-Dep) and Non-Deprived (ND) groups. Fig. 4A; Asterisk (*) indicates that rats in the CS+ groups responded significantly more than the No Odor groups for Rep-dep group during PSR sessions 1–4 and for ND group during session 1–3 (p <0.05). Plus (+) indicates that rats in the ND No Odor (PSR session 1), ND CS+ (PSR session 1–3) , Rep-Dep No Odor (PSR session 1 −2), and Rep-Dep CS+ (PSR sessions 1–4) groups responded significantly more on the lever previously associated with EtOH during PSR testing than extinction baseline (Ext Base) (p <0.05). Fig. 4B; Depicts the mean (±S.E.M.) responses per 10-min blocks on the lever previously associated with the delivery of EtOH in the ND No Odor group, ND CS+ group, Rep-Dep No Odor group, and Rep-Dep CS+ group during the first PSR session. Asterisk (*) indicates rats in the Rep-Dep CS+ group responded significantly (p < 0.05) more on the EtOH lever during the 1^st, 2^nd and 4^th 10-min blocks of PSR testing compared to all other groups. Pound (#) indicates that the ND No Odor and Rep-Dep No Odor groups responded significantly (p < 0.05) more on the EtOH lever during the 6^th 10-min block compared to the ND CS+ and the Rep-Dep CS+ groups.

Figure 5:

Depicts the mean (±S.E.M.) responses on the lever previously associated with the delivery of EtOH in Repeatedly Deprived (Rep-Dep) P rats that were exposed to CS+, CS⁰, and CS- in the non-drug paired environment then tested for PSR expression in the presence of CS+ (Fig. 5A) or CS- (Fig. 5B) in drug-paired environment. Fig. 5A; Asterisk (*) indicates that Rep-Dep rats, exposed to CS+ in the non-drug paired environment, responded significantly more than the CS⁰ and CS- during sessions 1–3, and the CS⁰ group responses were significantly higher than CS- during sessions 1–3 (p <0.05). Plus (+) indicates that Rep-Dep rats lever responding was significantly greater than extinction baseline (p <0.05) for CS+ and CS⁰ groups during PSR sessions 1–3 and CS- rats lever responding was significantly lower than extinction baseline (Ext Base) (p <0.05) during PSR session 2–3. Fig. 5B; There were no significant differences found for any of the groups.

Figure 6:

Depicts the mean (±S.E.M.) responses per session on the lever previously associated with the delivery of EtOH in Non–Deprived (ND) P rats that were exposed to CS+, CS⁰ and CS- in the non-drug paired environment then tested for PSR expression in the presence of CS+ (Fig. 6A) or CS- (Fig. 6B) in the drug-paired environment. Fig. 6A; Asterisk (*) indicates CS+ group was responding more than the CS⁰ and No Odor groups during PSR session 1 (p < 0.05). The CS⁰ and No Odor responded more than the CS- group during PSR session 1 (p < 0.05). Pound (#) indicates that during the 2^nd PSR test session responding in rats pretreated with the CS+ responded more than the No Odor group which responded more than the CS⁰ and CS- groups (p < 0.05). Dagger (†) indicates that during the 3^rd PSR test session, rats pretreated with the CS+ responded more than all other groups (p < 0.05). Plus (+) indicates that rats lever responding was significantly greater than extinction baseline (Ext Base) (p <0.05) for CS+ during PSR sessions 1–3, CS⁰ during PSR session 1, and for No Odor group during PSR session 1–2 (p <0.05). Fig. 6B; Asterisk (*) indicates that CS+ responding was less than the CS⁰ and CS- during PSR session 1 (p < 0.05).

Figure 7.

Depicts the mean (±S.E.M.) responses on the lever previously associated with the delivery of EtOH in P rats that were exposed to CS+ CS⁰ and CS- in the non-drug paired environment then tested for PSR expression in the absence of CS in the drug-paired environment following a 2, 4 and 8- hour delay. Upper Panel: The asterisks (*) indicates that during the 1^st and 2^nd PSR sessions, the 2-hour delay CS+ group responding on the lever previously associated with EtOH was significantly higher than the 2-hour CS⁰ and 2-hour CS- groups (p < 0.05). The 2-hour CS⁰ responding on the lever previously associated with EtOH was significantly higher than CS- group (p < 0.05). In addition, the 2-hour CS+ group lever responding was greater for the 1^st and 2^nd PSR sessions compared to extinction baseline (Ext Base), while the CS⁰ 2-hour group lever responding was only significant for the PSR session 1 compared to extinction baseline (p <0.05). Middle Panel: The asterisks (*) indicates that, during the 1^st PSR session, the 4-hour delay CS+ group responded significantly more than the 4-hour CS⁰ and 4-hour CS- groups (p < 0.05). The 4-hour CS⁰ responding on the lever previously associated with EtOH was significantly higher CS- group (p < 0.05). In addition, the 4-hour CS+ and CS⁰ group lever responding was greater for the 1^st PSR sessions compared to extinction baseline (Ext Base) (p <0.05). Lower Panel: There were no significant differences found for any of the groups following the 8-hour delay.