Neuroscience

Opioids and Drink

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Science  20 Feb 2009:
Vol. 323, Issue 5917, pp. 984-985
DOI: 10.1126/science.323.5917.984d

Substance abusers score higher on measures of cognitive and motor impulsivity. Cognitive impulsivity refers to the inability to delay gratification, whereas motor impulsivity, or disinhibition, describes the inability to withhold a pre-potent response. Animal studies confirm that impulsivity correlates with drug intake, although nearly all of these studies have examined impulsivity in relationship to psychostimulant drugs.

Olmstead et al. have investigated whether deletion of the μ- or δ-opioid receptor genes alters motor impulsivity in mice. They tested the behavior of these mutant animals in an operant-based behavioral task that assesses the ability of mice to withhold a well-learned pre-potent response (a nose poke used to gain a sucrose reward); the reward can be obtained only when nose-poke responses are made during a brief light stimulus. Mice lacking μ-opioid receptors exhibited decreased motor impulsivity, whereas those lacking δ-opioid receptors showed increased motor impulsivity. Additionally, mice lacking μ-opioid receptors were insensitive to the effects of alcohol, which increases impulsivity and decreases conditioned responding in wild-type mice, and the behavior of mice lacking δ-opioid receptors was completely disrupted by alcohol. Taken all together, these results indicate a link between opiate receptors in the brain, impulsive behavior, and behavior directed toward ingesting alcohol. — PRS

PLoS ONE 4, e4410 (2009).

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