Black tea improves attention and self-reported alertness.

Tea has previously been demonstrated to better help sustain alertness throughout the day in open-label studies. We investigated whether tea improves attention and self-reported alertness in two double-blind, randomised, placebo-controlled, crossover studies. Participants received black tea (made from commercially available tea bags) in one condition and placebo tea (hot water with food colours and flavours) similar in taste and appearance to real tea in the other condition. Attention was measured objectively with attention tests (the switch task and the intersensory-attention test) and subjectively with a self-report questionnaire (Bond-Lader visual analogue scales). In both studies, black tea significantly enhanced accuracy on the switch task (study 1 p<.002, study 2 p=.007) and self-reported alertness on the Bond-Lader questionnaire (study 1 p<.001, study 2 p=.021). The first study also demonstrated better auditory (p<.001) and visual (p=.030) intersensory attention after black tea compared to placebo. Simulation of theanine and caffeine plasma time-concentration curves indicated higher levels in the first study compared to the second, which supports the finding that tea effects on attention were strongest in the first study. Being the second most widely consumed beverage in the world after water, tea is a relevant contributor to our daily cognitive functioning.

The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness.

The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

A social conflict increases EEG slow-wave activity during subsequent sleep.

Electroencephalogram (EEG) slow-wave activity (SWA) during non-rapid eye movement (NREM) sleep is widely viewed as an indicator of sleep debt and sleep intensity. In a previous study, we reported a strong increase in SWA during NREM sleep after a social conflict in rats. To test whether this increase in SWA reflects normal physiological sleep or an unrelated by-product of the stress, we now measured the effect of a conflict in combination with extended sleep deprivation by means of gentle handling. We anticipated that if the social defeat-induced SWA reflects a true sleep debt, the drive for it would persist during the extended wakefulness. Male rats were subjected to a 1-h social conflict followed by 5 h of sleep deprivation by gentle handling or to 6 h gentle handling alone. The manipulations took place during the second half of the dark phase and recovery sleep was recorded during the subsequent light phase. Neither of the two procedures caused a significant change in the total duration of NREM or REM sleep thereafter. Yet, both modes of sleep deprivation induced a strong increase in SWA during NREM sleep. This SWA was significantly higher for 6 h after sleep deprivation consisting of a social conflict followed by gentle handling, as compared to sleep deprivation by handling alone. Thus, the SWA increasing effect of the conflict persisted during the extended wakefulness. The data confirm that social defeat stress accelerates the build up of sleep debt and support the notion that sleep debt and subsequent NREM sleep intensity not only depend on the duration of prior wakefulness but also on what animals experience during that waking.

Time course of chronic diazepam effects on the auditory evoked potential of the rat.

The time course of chronic diazepam effects on auditory evoked potentials was studied in rats. Auditory evoked potentials were elicited by background and target tones in a passive oddball paradigm. Diazepam was administered by slow release implants to establish constant blood concentrations. Recordings were made during 21 days of treatment and 9 days after treatment ceased. Diazepam increased the amplitude of the P40 component and decreased the amplitude of the P72-P102 components elicited by background tones. Diazepam increased the amplitude of the P40-P48 component and decreased that of the N58 component elicited by target tones. These effects remained constant during treatment. Diazepam further decreased the amplitude of the P102 component elicited by target tones. This effect became more distinct over time. No group differences were found 9 days after treatment. The constant drug effects on middle-latency components (P40-P48) might reflect diazepam-induced changes in sensory information processing. The decreased long-latency component (P102) might reflect a diminished attention to, or discrimination of, target tones. The time course of this effect might reflect diazepam-enhanced habituation.

Determination of the underivatized antineoplastic drugs cyclophosphamide and 5-fluorouracil and some of their metabolites by capillary gas chromatography combined with electron-capture and nitrogen-phosphorus selective detection.

A rapid and sensitive method for the determination of cyclophosphamide (CP) and 5-fluorouracil (5-FU) and some of their metabolites in one analysis has been developed. Surface-coated open-tubular OV-275 columns were combined with electron-capture detection and nitrogen-phosphorus selective detection. The influence of the column diameter on the separation is shown. Extraction with 2-propanol-diethyl ether (22:77) allows the isolation of CP, 5-FU and their analogues in one extraction step. The assay was applied to some pharmacokinetic experiments with chemotherapeutically treated patients and with a WAG/Rij rat.