ArticlePsychopharmacology2025
Alternating self-administration sessions of cocaine and heroin impact drug-related motivation and vocalisations in rats.
Article in Psychopharmacology, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
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Who cites it
2 citing papers in PubMed.
- Can the incentive-sensitization theory of addiction incorporate addiction to opioid drugs?Psychopharmacology · 2026Review
- Interrogating roles for VTA dopamine neurons in locomotion and ultrasonic vocalizations elicited by different classes of rewarding drugs.Psychopharmacology · 2026Article
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4 authors.
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Abstract
rationaleAnimal models of addiction often study changes in motivation after repeated self-administration of a single drug. However, human users frequently consume multiple drugs, potentially altering their motivation and affective response.
objectivesThis study investigated how individual rats differentially self-administer cocaine and heroin, and whether motivation to take each drug was associated with affective states, as indicated by ultrasonic vocalisations (USVs). We also determined whether opioid antagonism (via naltrexone), which is known to decrease heroin-taking and associated USVs, also altered motivation and vocalisations for cocaine.
methodsMale Lister Hooded rats, with surgically implanted catheters, self-administered cocaine and heroin on alternating days. Motivation was evaluated via drug intake escalation (fixed-ratio schedule), behavioural adaptation to dose reductions (behavioural economics), and progressive ratio breakpoints (with or without naltrexone). USVs were recorded and analysed using machine learning software (DeepSqueak).
resultsRats escalated intake of both drugs during training. At the start of each session, rats rapidly self-administered cocaine or heroin; this drug-loading behaviour was associated with an increase in 50 kHz vocalisations. Rats altered their cocaine and heroin intake when drug doses decreased, and this was accompanied by reduced 50 kHz USVs. Lastly, naltrexone reduced progressive ratio breakpoints for heroin but not cocaine; naltrexone also decreased 50 kHz USVs for heroin (an effect which persisted).
conclusionsDistinct patterns emerged in motivation and USVs between cocaine and heroin self-administration. Notably, USV frequency did not consistently align with motivation, especially when drug dosage changed. Future research may clarify this divergence.
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