Decreased consumption of natural rewards in rhesus monkeys with prolonged methamphetamine abstinence
J. ZhouIntroduction
Relapse to drug use is a major clinical challenge in the treatment of addictive disorders, including psychostimulant use and may be exacerbated by reduced sensitivity to natural, non-drug reward. Given the relatively limited set of outcomes, and short withdrawal time in rodent studies, we conducted a more detailed assessment of the response to natural rewards in methamphetamine (METH) naive versus exposed monkeys during long-term abstinence.
Objectives
This study introduced an improved sucrose preference test (iSPT) to assess natural reward seeking and consumption in monkeys with long-term abstinence after methamphetamine (METH) use. The test was administered to sixteen naive monkeys and five METH exposed monkeys that had been abstinent for at least 3 months.
Methods
Sixteen naive monkeys without being exposed to METH and five METH exposed monkeys abstinent for at least three months were studied during a withdrawal period and subjected to improved sucrose preference test (iSPT) and sucrose preference test (SPT). The improved paradigm assessed sucrose preference scores and three behavioral indicators extracted from video recordings. These behavioral indicators were supposed to reflect different dimensions of approach behaviors and consumption in both animal groups.
Results
METH exposed monkeys showed a lower sucrose preference score in both the iSPT (z = -2.10, p = 0.036) and the sucrose preference test (z = -2.61, p =0.009). The sucrose preference score was significantly correlated with the latency of the establishment of stable sucrose-preference (r = -0.76, df = 46, p < 0.001) but not with the other variables. Furthermore, water-sucrose switch latency and switch times were significantly negatively correlated (r = -0.50, df = 20, p = 0.02).
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