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  • 1
    ISSN: 1432-1041
    Keywords: Key words Caffeine ; Cocoa ; Chocolate ; Theobromine; methylxanthines ; absorption ; humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To compare caffeine and theobromine absorption after oral administration of capsules, cola beverage and chocolate candy. Methods: Three males and four females who abstained from methylxanthines received five methylxanthine-containing treatments: caffeine in capsules (72 mg), administered twice; theobromine in capsules (370 mg); cola beverage (72 mg caffeine) and chocolate candy (72 mg caffeine and 370 mg theobromine). Plasma methylxanthine levels were assayed from samples collected before and 0.25, 0.50, 0.75, 1.0, 1.5, 2.0, and 3.0 h after caffeine capsule and cola treatments and, additionally, at 4.0 and 6.0 h after theobromine capsule and chocolate treatments. Results: Caffeine plasma concentrations increased rapidly and peaked at approximately 30 min following both capsule treatments 1 (Cmax: 1.93 μg ⋅ ml−1); and 2 (Cmax: 2.05 μg ⋅ ml−1). Relative to capsules, caffeine absorption from cola and chocolate was delayed and produced lower maximum caffeine plasma concentrations which peaked 1.5–2.0 h after treatment (For cola, Cmax: 1.57 μg ⋅ ml−1); and for chocolate, Cmax: 1.50 μg ⋅ ml−1. Theobromine plasma concentrations peaked approximately 3 h after capsule administration (Cmax: 6.72 μg ⋅ ml−1). Relative to capsules, theobromine absorption from chocolate was more rapid and produced higher maximum theobromine plasma concentrations which peaked approximately 2 h after treatment (Cmax: 8.05 μg ⋅ ml−1). Conclusions: The results suggest that a usual dietary portion of the cola or chocolate used in this study would produce behaviorally discriminable plasma levels of caffeine in most subjects and of theobromine in at least one subject.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Morphine tolerance ; Drug discrimination ; Schedule-controlled behavior ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The development of tolerance to the discriminative stimulus properties of morphine was examined in rats trained to discriminate saline and 3.2 mg/kg morphine under amultiple timeout 15 min, 5 min fixed-ratio 30 schedule of food delivery. Generalization gradients were generated by administering increasing doses of morphine before successive timeout periods within the experimental session. Over the course of the study, the minimal discriminable dose (MDD) of morphine under control conditions fluctuated but did not systematically increase or decrease. Acute pretreatments of 3.2–17.8 mg/kg morphine 4–24 h before a generalization test resulted in minor changes in the MDD. To examine development of tolerance, supplemental doses of morphine (17.8 mg/kg) or saline were administered twice daily while discrimination training was either suspended or continued. Tolerance was assessed by weekly generalization tests. Greater tolerance developed to the morphine stimulus when training was suspended than when training was continued. For both training conditions, response rates during generalization tests were markedly suppressed during supplemental morphine administration, and original generalization gradients were recaptured within 2 weeks after termination of supplemental morphine administration. Supplemental saline administration did not alter the discriminative or rate-altering effects of morphine under either training condition. Thus, the magnitude of tolerance to a morphine discriminative stimulus reflected an interaction of supplemental drug treatment with the training conditions imposed during that treatment.
    Type of Medium: Electronic Resource
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