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Effects of Daily Morphine Treatment on Impulsivity in Rats Responding under a 5‐Choice Serial Reaction Time Task
Author(s) -
Maguire David,
France Charles
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.769.7
Subject(s) - impulsivity , serial reaction time , delay discounting , morphine , opioid , psychology , cognition , anesthesia , medicine , developmental psychology , neuroscience , receptor
Impulsivity is thought to contribute to the persistence of opioid abuse. Repeated opioid treatment enhances some forms of impulsivity (e.g., delay discounting); however, it is unclear whether repeated opioid treatment enhances other forms of impulsivity such as behavioral inhibition. This study examined the effects of daily morphine treatment on responding under a 5‐choice serial reaction time task. Rats (n=5) detected a light presented randomly in one of 5 response holes. Nose‐pokes in the illuminated target hole (correct) delivered food, whereas failure to respond (omission), nose‐pokes in the incorrect hole, or nose‐pokes prior to illumination of the target hole (premature responses) initiated a time‐out. Impulsivity was indexed by the number of premature responses, that is, failures to inhibit a response until the target stimulus was presented. Morphine administered acutely (0.1‐10 mg/kg, i.p.) did not affect response accuracy, modestly increased premature responding, and dose‐dependently increased omissions. After 1 week of daily treatment with 10 mg/kg of morphine, tolerance developed to its effects on omissions, and premature responses increased from an average of 8 per session under baseline conditions to more than 30 per session. In some rats, premature responses increased more than 10‐fold. Moreover, during treatment, the morphine dose‐effect curve for premature responding shifted upwards, possibly reflecting increased effectiveness of morphine to induce premature responding and supporting the notion that repeated opioid administration enhances this form of impulsivity. Taken together with previous research, these data suggest opioid use increases impulsivity which could then play a role in promoting continued abuse and possibly relapse.