Methamphetamine attenuates disruptions in performance and mood during simulated night-shift work.
ABSTRACT Increased sleepiness while working and sleep disruptions are common complaints among shift workers. Consequently, shift workers may be more susceptible to diminished performance and work-related accidents.
To examine the effects of the central nervous system stimulant methamphetamine on psychomotor task performance, subjective effects, and food intake during shift work under laboratory conditions.
Seven participants completed this 23-day, within-participant design, residential laboratory study. They received a single oral methamphetamine dose (0, 5, 10 mg) 1 h after waking for three consecutive days under two shift conditions: (1) during the day shift, participants performed computerized psychomotor tasks from 0830 hours to 1730 hours and went to bed at 2400 hours and (2) during the night shift, participants performed tasks from 0030 hours to 0930 hours and went to bed at 1600 hours. Shifts alternated three times during the study; shift conditions were separated by an "off" day during which participants were not on a schedule and data were not collected.
When participants received placebo, psychomotor task performance and subjective effects were disrupted during the night shift, relative to the day shift. Changing shift conditions did not alter food intake significantly. Methamphetamine reversed performance and subjective-effects disruptions, and decreased food intake during the night shift.
These data indicate that shift changes produce performance impairments and mood alterations, and that a single low to moderate dose of methamphetamine attenuates many shift change-related disruptions in performance and mood.
- [Show abstract] [Hide abstract]
ABSTRACT: The circadian timing system influences a vast array of behavioral responses. Substantial evidence indicates a role for the circadian system in regulating reward processing. Here we explore time of day effects on drug anticipation, locomotor activity, and voluntary methamphetamine (MA) and food intake in animals with ad libitum food access. We compared responses to drug versus a palatable treat during their normal sleep times in early day (zeitgeber time (ZT) 0400) or late day (ZT 1000). In the first study, using a between-subjects design, mice were given daily 1-hr access to either peanut butter (PB-Alone) or to a low or high concentration of MA mixed in PB (MA+PB). In study 2, we repeated the experiment using a within-subjects design in which mice could choose between PB-Alone and MA+PB at either ZT 0400 or 1000. In study 3, the effects of MA-alone were investigated by evaluating anticipatory activity preceding exposure to nebulized MA at ZT 0400 vs. ZT 1000. Time of day effects were observed for both drug and palatable treat, such that in the between groups design, animals showed greater intake, anticipatory activity, and post-ingestional activity in the early day. Furthermore, there were differences among mice in the amount of MA ingested but individuals were self-consistent in their daily intake. The results for the within-subjects experiment also revealed robust individual differences in preference for MA+PB or PB-Alone. Interestingly, time of day effects on intake were observed only for the preferred substance. Anticipatory activity preceding administration of MA by nebulization was also greater at ZT 0400 than ZT 1000. Finally, pharmacokinetic response to MA administered intraperitoneally did not vary as a function of time of administration. The results indicate that time of day is an important variable mediating the voluntary intake and behavioral effects of reinforcers.Pharmacology Biochemistry and Behavior 05/2013; · 2.82 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Although not all individuals who work outside of standard daytime hours develop physical and psychiatric issues, there is a substantial portion of shift workers who develop shift work disorder. Shift work disorder is due to a misalignment between an individual's endogenous circadian rhythms and environmental stimuli, and can have potentially serious consequences to an individual's health and quality of life. This article reviews the neurobiological and genetic underpinnings of shift work disorder, and describes how desynchronization of the molecular clock may lead to both physical and psychiatric illnesses. Diagnostic tools and treatment guidelines to address the circadian misalignment, excessive sleepiness, and insomnia experienced by patients with shift work disorder are also discussed.CNS spectrums 12/2013; 18(s1):42-54. · 1.73 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Armodafinil is a medication used to treat excessive sleepiness in individuals with shift work disorder (SWD). In the present study, we investigate whether armodafinil can normalize nocturnal sleepiness in a group of typical SWD patients. Participants were 12 night workers (aged 33.8 ± 8.57 years, 7 female subjects) with excessive sleepiness (≥10 on the Epworth Sleepiness Scale; mean, 14.8 ± 3.16), meeting the International Classification of Sleep Disorders, Second Edition criteria for SWD, with no other sleep or medical disorders verified by polysomnogram. The multiple sleep latency test (MSLT) was not used as an entry criteria. Armodafinil was administered at 10:30 PM in a randomized, double-blind, placebo-controlled, crossover design with experimental nights separated by 1 week. Primary end point was the MSLT, with naps at 1:30, 3:30, 5:30, and 7:30 AM. Other study measures included a sleepiness-alertness visual analog scale administered before each nap, and 2 computer-based performance tests evaluating attention and memory. Subjects with SWD had a mean MSLT of 5.3 ± 3.25 minutes, indicating a mean level of pathological sleepiness. Armodafinil significantly improved MSLT score to 11.1 ± 4.79 minutes (P = 0.006). Subjective levels of alertness on the visual analog scale also improved (P = 0.008). For performance, reaction time to central (P = 0.006) and peripheral (P = 0.003) stimuli and free recall memory (P = 0.05) were also improved. Armodafinil 150 mg administered at the beginning of a night shift normalizes nocturnal sleepiness in individuals with SWD unselected for objective sleepiness. Subjective measures of sleepiness and cognitive performance are also improved. This suggests that armodafinil can improve levels of nocturnal alertness to within normal daytime levels in the majority of patients with SWD.Journal of clinical psychopharmacology 04/2014; · 5.09 Impact Factor