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Query: UMLS:C0085632 (apathy)
 4,089 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present experiments were designed to assess whether caffeine, a substance that potentiates human perception of some artificial sweeteners, might also enhance perception of such substances by rats. In Experiment 1, rats were given varied concentrations of saccharin, cyclamate, and caffeine in 2-choice tests. 'Indifference thresholds' for these substances were 3.9 X 10(-4) M, 1 X 10(-3) M, and 1.6 X 10(-7) M, respectively. In Experiment 2, concentrations of saccharin and cyclamate just above and below indifference were used as stimuli in a flavor avoidance learning (FAL) paradigm. 'Suprathreshold' concentrations of saccharin and cyclamate produced reliable FAL while 'subthreshold' concentrations did not. In Experiment 3, rats were exposed to a low concentration of caffeine followed by presentations of subthreshold concentrations of saccharin or cyclamate as stimuli in a FAL paradigm. Saccharin FAL was observed but cyclamate FAL was not, suggesting that caffeine preexposure selectively potentiated detection of saccharin. In Experiment 4, animals were given saccharin or cyclamate with or without prior exposure to caffeine in a FAL paradigm. During subsequent tests, animals were presented with saccharin or cyclamate following exposure to caffeine saccharin or cyclamate mixed with caffeine saccharin or cyclamate alone. Saccharin FAL was observed following caffeine preexposure, but mixing with caffeine had no effect. These findings of selective potentiation are consistent with previous studies of human sensitivity after caffeine preexposure. Moreover, the present results support the notion that inhibitory A1 adenosine receptors are involved in modulating the perceived intensity of some flavors.
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PMID:Caffeine enhancement of saccharin but not cyclamate flavor avoidance. 244 67

A recent major theory was that a meal high in carbohydrate increased the rate that tryptophan enters the brain, leading to an increase in the level of the neurotransmitter serotonin that modulates mood. Although such a mechanism may be important under laboratory conditions it is unlikely to be of significance following the eating of any typical meal. As little as 2-4% of the calories of a meal as protein will prevent an increased availability of tryptophan. Arguably the food with the greatest impact on mood is chocolate. Those who crave chocolate tend to do so when they feel emotionally low. There have been a series of suggestions that chocolate's mood elevating properties reflect 'drug-like' constituents including anandamines, caffeine, phenylethylamine and magnesium. However, the levels of these substances are so low as to preclude such influences. As all palatable foods stimulate endorphin release in the brain this is the most likely mechanism to account for the elevation of mood. A deficiency of many vitamins is associated with psychological symptoms. In some elderly patients folate deficiency is associated with depression. In four double-blind studies an improvement in thiamine status was associated with improved mood. Iron deficiency anaemia is common, particularly in women, and is associated with apathy, depression and rapid fatigue when exercising.
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PMID:The effects of nutrients on mood. 1061 80

Animals make use of contact chemoreception structures to examine the quality of potential food sources. During this evaluation they can detect nutritious compounds that promote feeding and recognize toxins that trigger evasive behaviors. Although animals can easily distinguish between stimuli of different gustatory qualities (bitter, salty, sweet, etc.), their ability to discriminate between compounds of the same quality may be limited. Numerous plants produce alkaloids, compounds that elicit aversive behaviors in phytophagous insects and almost uniformly evoke a bitter taste for man. In hematophagous insects, however, the effect of feeding deterrent molecules has been barely studied. Recent studies showed that feeding in Rhodnius prolixus can be negatively modulated by the presence of alkaloids such as quinine (QUI) and caffeine (CAF), compounds that elicit similar aversive responses. Here, we applied associative and non-associative learning paradigms to examine under two behavioral contexts the ability of R. prolixus to distinguish, discriminate and/or generalize between these two bitter compounds, QUI and CAF. Our results show that bugs innately repelled by bitter compounds can change their behavior from avoidance to indifference or even to preference according to their previous experiences. After an aversive operant conditioning with QUI or CAF, R. prolixus modified its behavior in a direct but also in a cross-compound manner, suggesting the occurrence of a generalization process between these two alkaloids. Conversely, after a long pre-exposure to each alkaloid, bugs decreased their avoidance to the compound used during pre-exposure but still expressed an avoidance of the novel compound, proving that QUI and CAF are detected separately. Our results suggest that R. prolixus is able to discriminate between QUI and CAF, although after an associative conditioning they express a symmetrical cross-generalization. This kind of studies adds insight into the gustatory sense of a blood-sucking model but also into the learning abilities of hematophagous insects.
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PMID:Kissing bugs can generalize and discriminate between different bitter compounds. 2786 72