Effects of Mu-Opioid Receptors on Addictive Behaviors
Fedolak, Allison C.
The role of knocked out mu-opioid receptors was investigated on taste reactions and locomotor activity in this study. Three different genotype strains of mice (mu-receptor knockout, heterozygote and wildtype) were examined. Each group was given a small concentration of sucrose (0.0 M, 0.01 M, 0.1 M, and 1.0 M). Using taste reactivity analysis, the reactions to their drinking bouts were recorded, to determine the type of reaction encountered (hedonic, neutral or aversive). Locomotor activity was recorded by analyzing the amount of nose pokes and rearings exhibited by the mice. Results show that there was a significant effect for mu-opioid knockout receptor mice and a greater number of aversive reactions across sucrose concentrations, compared to heterozygote and wildtype mice. There was a significant effect for mu-opioid receptor knockout mice and hedonic taste reactions, showing that there was a decrease of hedonic reactions compared to heterozygote and wildtype mice. There were no significant effects for neutral taste reactions and locomotor activity. The data suggest that there is a "disliked" effect for muopioid knockout mice. This means that there is a difference in a "wanted" and "liked" behavior in relation to mu-opioid receptors. These results could imply that there is a link between "liked" behavior and addiction.
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