University of Tasmania
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Reinforcing and anxiolytic-like effects of alcohol in planaria require ˜í¬¿-opioid receptor activation

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posted on 2023-05-28, 00:25 authored by Read, TJ
Planaria have been used for decades as subjects for psychopharmacology research, predominantly in addiction studies involving dopamine agonists. However, this research largely focused on classical conditioning, with comparatively few studies examining how planaria behaviour is altered by alcohol administration. In humans and other mammals, ethanol enhances dopamine transmission via endogenous opioid release. This study sought to investigate the link between ethanol and endogenous opioids in planaria in a novel operant conditioning paradigm and avoidance task. Study 1 was used to determine whether 1% or 2% ethanol concentrations induced significant conditioning, with 2% showing greater effectiveness. Study 2 investigated operant conditioning with ethanol (2%), finding significant results after 4 days of reinforcement. Study 3 investigated whether the mu-opioid receptor antagonist naloxone affected conditioning induced by ethanol. Results indicated that naloxone blocked the acquisition of discrimination learning with 2% ethanol, suggesting that alcohol reinforcement in planaria necessitates mu-opioid receptor activation. Study 4 investigated the anxiolytic effect of ethanol in planaria, finding significant increases in light tolerance when ethanol was administered. These novel results indicate that planaria are a valuable animal model for ethanol research and that potential future alcohol abuse medications might be validly tested in this species for preliminary efficacy studies.


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