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Daily morphine administration increases impulsivity in rats responding under a 5-choice serial reaction time task
D R Maguire1, C Henson1, C P France1,2
1Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
British Journal of Pharmacology
|January 19, 2016
Summary
Repeated morphine administration increased motor impulsivity in rats, a key factor in drug abuse risk. Tolerance developed to other effects, but motor impulsivity worsened with daily opioid agonist use.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
Background:
- Opioid agonists, like morphine, can increase impulsivity, particularly delay discounting.
- The impact of repeated opioid agonist administration on motor impulsivity remains largely unexamined.
Purpose of the Study:
- To investigate the effects of acute and repeated morphine administration on motor impulsivity in rats.
- To assess whether tolerance develops to the motor impulsivity-enhancing effects of morphine.
Main Methods:
- Rats were trained on a five-choice serial reaction time task, with premature responding serving as the index of motor impulsivity.
- The effects of acute morphine and amphetamine were assessed before and during daily morphine administration over three weeks.
Main Results:
- Acute morphine increased omissions and premature responding; amphetamine increased premature responding.
- Following three weeks of daily morphine, tolerance developed to its effects on omissions.
- Motor impulsivity, measured by premature responding, significantly increased with repeated morphine administration.
Conclusions:
- Repeated morphine administration enhances motor impulsivity, despite tolerance to other effects.
- Increased impulsivity due to opioid agonist use may elevate the risk for drug abuse.
