The dopamine system is important for incentive salience attribution, where motivational value is assigned to conditioned cues that predict appetitive reinforcers. However, the role of dopamine in this process may change with extended training. We tested the effects of dopamine D1-like and D2-like receptor antagonism on the expression of sign-tracking and goal-tracking conditioned responses following extended Pavlovian conditioned approach (PCA) training. We also tested if amphetamine-induced psychomotor sensitization accelerates the enhanced acquisition of sign-tracking that is observed with extended training. In experiment 1, 24 male Long-Evans rats received 20 PCA sessions in which one lever (CS+, 10 s) predicted 0.2 mL sucrose (10%, w/v) delivery and the other lever (CS-) did not. SCH-23390 (D1-like antagonist) or eticlopride (D2-like antagonist) were administered before non-reinforced behavioural tests at doses of 0, 0.01, and 0.1 mg/kg (s.c.). In experiment 2, rats received vehicle or 2 mg/kg amphetamine (i.p.) for 7 days (n = 12/group). Ten days later, they received 16 PCA training sessions. Both doses of SCH-23390 reduced sign-and goal-tracking, but also reduced locomotor behaviour. A low dose of eticlopride (0.01 mg/kg) selectively reduced goal-tracking, without affecting sign-tracking or locomotor behaviour. Amphetamine produced psychomotor sensitization, and this did not affect the acquisition of sign-or goal-tracking. Following extended PCA training, dopamine D2-like receptor activity is required for the expression of goal-tracking but not sign-tracking. Psychomotor sensitization to amphetamine did not impact incentive salience attribution; however, more selective manipulations of the dopamine system may be needed.

Individual or singly-housing laboratory rats is common in many animal facilities, but has an adverse impact on the welfare of this social species. It has previously been shown that a small proportion of individually housed mice (∼5%) engage in pathological overgrooming behaviour, but this has not been assessed in rats. We performed an observational study to determine the prevalence of overgrooming-related self-injury and whether providing nesting material enrichment throughout an animal’s life would affect the prevalence or severity of overgrooming-related self-injury. Due to protocol differences between projects in our behavioural neuroscience lab, unenriched rats received a nylabone and a shelter ( n = 167), while baseline-enriched rats received a nylabone, shelter and shredded paper nesting material throughout experiments ( n = 238). Unenriched rats received nesting material enrichment after the onset of overgrooming-related self-injury. Over 18 months, rats were monitored by their experimenters on a daily basis (5–7 days/week over 2–3 months/project) and any cases of overgrooming-related self-injury were recorded. Replicating the findings of previous studies in mice, we observed 20 cases of overgrooming-related self-injury (∼5%) with no difference in prevalence between rats on the basis of supplier, cage position, experimental procedure (behavioural only or involving surgical procedures), reinforcer (ethanol or sugar) or level of baseline-enrichment. While there was no difference in onset severity between rats that were unenriched at baseline and baseline-enriched rats, baseline-enriched rats had lower self-injury severity scores at one-, two- and four-week follow-ups. These results suggest that nesting material enrichment provided throughout an animal’s life may reduce overgrooming-related self-injury.

Vendor differences are thought to affect Pavlovian conditioning in rats. After observing possible differences in sign-tracking and goal-tracking behaviour with rats from different breeding colonies, we performed an empirical replication of the effect. 40 male Long-Evans rats from Charles River colonies ‘K72’ and ‘R06’ received 11 Pavlovian conditioned approach training sessions (or “autoshaping”), with a lever as the conditioned stimulus (CS) and 10% sucrose as the unconditioned stimulus (US). Each 58-min session consisted of 12 CS-US trials. Paired rats (n = 15/colony) received the US following lever retraction. Unpaired control rats (n = 5/colony) received sucrose during the inter-trial interval. Next, we evaluated the conditioned reinforcing properties of the CS, by determining whether rats would learn to nose-poke into a new, active (vs. inactive) port to receive CS presentations alone (no sucrose). Preregistered confirmatory analyses showed that during autoshaping sessions, Paired rats made significantly more CS-triggered entries into the sucrose port (i.e., goal-tracking) and lever activations (sign-tracking) than Unpaired rats did, demonstrating acquisition of the CS-US association. Confirmatory analyses showed no effects of breeding colony on autoshaping. During conditioned reinforcement testing, analysis of data from Paired rats alone showed significantly more active vs. inactive nosepokes, suggesting that in these rats, the lever CS acquired incentive motivational properties. Analysing Paired rats alone also showed that K72 rats had higher Pavlovian Conditioned Approach scores than R06 rats did. Thus, breeding colony can affect outcome in Pavlovian conditioned approach studies, and animal breeding source should be considered as a covariate in such work.

Background and Aims: Experiencing higher rates of stigma, marginalization and discrimination puts transgender individuals at risk for alcohol use and associated harms. Measures of harmful drinking were designed with cisgender people in mind, and some rely on sex-and gender-based cut-offs. The applicability of these measures for gender diverse samples remains unknown. The present study had two aims: (i) identify gendernon-inclusive language and cut-offs in measures of harmful drinking, and (ii) systematically review research reporting psychometric properties of these measures in transgender individuals. Methods:We reviewed 22 measures of harmful drinking for gendered language and sexand gender-based cut-off values and provided suggestions for revision when warranted.We also conducted a systematic narrative review, including eight eligible studies, summarizing the psychometric properties of measures of harmful drinking in transgender populations.Results: Six of 22 measures of harmful drinking were not gender inclusive, because of gendered language in the measure itself or use of sex-or gender-based cut-off scores.Only eight published studies reported psychometric data for these measures in transgender people. Apart from in one study, the Alcohol Use Disorders Identification Test (AUDIT) and Alcohol Use Disorders Identification Test Consumption (AUDIT-C) appear reliable for transgender adults (Cronbach's α: AUDIT [0.81-0.87] and AUDIT [0.72- 0.8)]). There is initial support for using uniform cut-offs for transgender people for the AUDIT-C (≥3) and binge drinking (≥5 drinks in a sitting).Conclusions: Most existing measures of harmful drinking appear to be gender inclusive (containing gender neutral language and uniform cut-off scores across sex and gender groups) and some that are not easily adapted to be gender inclusive.

Rationale. The dopamine system is thought to be important in incentive salience attribution, where motivational value is assigned to a cue that predicts an appetitive reinforcer (sign-tracking), however, dopamine's role may change with extended training. Objectives. We tested the effects of selective dopamine D1-like and D2-like receptor antagonism on the expression of Pavlovian conditioned approach after extended Pavlovian conditioned approach (PCA) training. We also tested the hypothesis that locomotor sensitization would accelerate the phenotypic shift to sign-tracking. Methods. 24 male Long-Evans rats were subjected to 20 PCA sessions in which one lever (CS+, 10 s) predicted 0.2 mL sucrose delivery and the other lever (CS-) did not. SCH-23390 or eticlopride were administered prior to behavioral tests at doses of 0, 0.01, and 0.1 mg/kg (s.c.). In a subsequent experiment, rats were exposed to vehicle or 2 mg/kg amphetamine (i.p.) for 7 days (n = 12/group). After a 10-day incubation period, they were subjected to PCA training for 16 sessions. Results. The D1 antagonist SCH-23390 reduced locomotor activity and port entries during inter-trial intervals, but the D2 antagonist eticlopride selectively reduced CS+ port entries in goal-trackers , i.e. animals motivated towards the reinforcer. Locomotor sensitization had no effect on the acquisition of sign-tracking. Conclusions. A commonly used dose of SCH-23390 exhibited off-target locomotor effects and D2 receptors were not required for expression of sign-tracking after extended training. Amphetamine-induced locomotor sensitization did not enhance acquisition of sign-tracking behavior, suggesting that the sensitivity of the dopamine system does not drive acquisition of sign-tracking behavior.