Increased impulsive choice for saccharin during PCP withdrawal in female monkeys: influence of menstrual cycle phase
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In previous studies with male and female rhesus monkeys, withdrawal of access to oral phencyclidine (PCP) self-administration reduced responding for food under a high fixed-ratio (FR) schedule more in males than females, and with a delay discounting (DD) task with saccharin (SACC) as the reinforcer impulsive choice for SACC increased during PCP withdrawal more in males than females.
The goal of the present study was to examine the effect of PCP (0.25 or 0.5 mg/ml) withdrawal on impulsive choice for SACC in females during the follicular and luteal phases of the menstrual cycle.
Materials and methods
In component 1, PCP and water were available from two drinking spouts for 1.5 h sessions under concurrent FR 16 schedules. In component 2, a SACC solution was available for 45 min under a DD schedule. Monkeys had a choice of one immediate SACC delivery (0.6 ml) or six delayed SACC deliveries, and the delay was increased by 1 s after a response on the delayed lever and decreased by 1 s after a response on the immediate lever. There was then a 10-day water substitution phase, or PCP withdrawal, that occurred during the mid-follicular phase (days 7–11) or the late luteal phase (days 24–28) of the menstrual cycle. Access to PCP and concurrent water was then restored, and the PCP withdrawal procedure was repeated over several follicular and luteal menstrual phases.
PCP deliveries were higher during the luteal (vs follicular) phase. Impulsive choice was greater during the luteal (vs follicular) phase during withdrawal of the higher PCP concentration.
PCP withdrawal was associated with elevated impulsive choice for SACC, especially in the luteal (vs follicular) phase of the menstrual cycle in female monkeys.
KeywordsDelay discounting Follicular phase Impulsive choice Luteal phase Menstrual cycle Phencyclidine (PCP) Rhesus monkeys Saccharin (SACC) Withdrawal
The authors are grateful to John Eckstrom and Lisa Tsackert for their technical assistance and Natalie Zlebnik for reviewing an earlier version of this manuscript and assisting with the figures. This research was supported by the National Institute on Drug Abuse grants R01 DA002486-32 and K05 DA015267-10 (MEC).
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