Physiology & behavior
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Physiology & behavior · Jun 2006
Comparative StudyInfluence of nitric oxide on morphine-induced amnesia and interactions with dopaminergic receptor agents.
The interactions of dopaminergic receptors and nitric oxide (NO) with morphine-induced memory of passive avoidance have been investigated in mice. Pre-training administration of morphine (1, 3 and 5 mg/kg, s.c.) dose-dependently decreased the learning of a one-trial passive avoidance task. Pre-training administration of L-arginine, a nitric oxide precursor (50, 100 and 200 mg/kg, i.p.), alone did not affect memory formation. ⋯ On the other hand, the inhibition of morphine-induced amnesia by L-arginine (200 mg/kg, i.p.) was significantly decreased by pretreatment with different doses of dopamine D1 receptor antagonist, SCH 23390 (0.001, 0.01 and 0.1 mg/kg, i.p.) or D2 receptor antagonist, sulpiride (12.5, 25, 50 and 100 mg/kg, i.p.). However, the dopamine receptor antagonists could not affect memory formation by themselves. It may be concluded that the morphine-induced impairment of memory formation can be prevented by nitric oxide donor and, in this effect, dopaminergic mechanism is involved.
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Physiology & behavior · Jun 2006
Comparative StudyLimbic and HPA axis function in an animal model of chronic neuropathic pain.
Chronic pain can be considered a form of chronic stress, and chronic pain patients often have disturbances of the hypothalamic-pituitary-adrenal (HPA) axis, including abnormal cortisol levels. In addition, chronic pain patients have an increased incidence of depression and anxiety, stress-related disorders that are frequently accompanied by disturbances in the limbic system (e.g. hippocampus and amygdala) and the HPA axis. Despite the fact that the literature supports a strong link between chronic pain, stress disorders, and limbic dysfunction, the mechanisms underlying the effects of chronic pain on the HPA axis and limbic system are not understood. ⋯ CCI increased the expression of corticotrophin releasing hormone mRNA in the central amygdala, and not the paraventricular nucleus of the hypothalamus or the bed nucleus of the stria terminalis. Moreover, glucocorticoid receptor mRNA expression in CCI rats was increased in the medial and central amygdala, unaffected in the paraventricular nucleus, and decreased in the hippocampus. These results suggest that increased nociceptive sensitivity during chronic pain is associated with alterations in the limbic system, but is dissociated from HPA axis activation.
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Physiology & behavior · Apr 2006
Comparative StudyModel for predicting and phenotyping at normal weight the long-term propensity for obesity in Sprague-Dawley rats.
Tests were conducted to determine whether weight gain or nutrient intake measures during the first week of exposure to a macronutrient diet can accurately predict an animal's long-term propensity towards obesity. In multiple groups of normal-weight Sprague-Dawley rats (n=35-70/group), daily weight gain during the first 5 days on a high-fat diet (45-60% fat) was found to be strongly, positively correlated (r=+0.71 to r=+0.82) with accumulated body fat in 4 dissected depots after 4-6 weeks on the diet. This measure consistently identified obesity-prone (OP) rats which, relative to the obesity-resistant (OR) rats, were only slightly heavier (+15 g, 4%) and hyperphagic (+9 kcal, 8%) after 5 days but markedly heavier (+70g) with up to 2-fold greater fat mass after several weeks on the diet. ⋯ These included elevated leptin, insulin, triglycerides and glucose, along with increased lipoprotein lipase activity (LPL) in adipose tissue and galanin expression in the paraventricular nucleus. Most notable were significant reductions in muscle of LPL activity and ratio of beta-hydroxyacyl-CoA dehydrogenase to citrate synthase activity, indicating a decline in lipid transport and capacity of muscle to metabolize lipids. By occurring early with initial weight gain, these hypothalamic and metabolic disturbances in OP rats, favoring fat storage in adipose tissue over fat oxidation in muscle, may have causal relationships to long-term accumulation of body fat.
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Physiology & behavior · Mar 2006
Randomized Controlled TrialEffects of transdermal nicotine on attention in adult non-smokers with and without attentional deficits.
Extant evidence suggests a possibility of self-medication to account for greater prevalence of cigarette smoking among adults with ADHD as they tend to show improvements on affective and cognitive measures, particularly on measures of sustained attention following nicotine administration. The present study was conducted to evaluate whether adult non-smokers with low attentiveness might exhibit greater improvements on measures of sustained attention than those with higher attentiveness using neuropsychological tests that had previously shown sensitivity to ADHD. On the basis of their scores on attention scales used in the diagnosis of adult ADHD, 62 male non-smokers were divided into 2 groups of either low or high attentiveness and treated with either a placebo or 7 mg nicotine patch. ⋯ On the Conners' CPT participants in the low attention group treated with nicotine committed significantly fewer errors of commission, showed improved stimulus detectability and fewer perseverations than those in the low attention placebo group. On the WCST nicotine significantly impaired the ability of participants in the high attention group to learn effective strategies to complete the test with fewer trials. The results showed nicotine-induced improvement on some measures of sustained attention in the low attention group and some decrement in working memory in the high attention group, which suggests that nicotine tends to optimize rather than improve performance on cognitive tasks.
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Physiology & behavior · Feb 2006
Clinical TrialBitter taste markers explain variability in vegetable sweetness, bitterness, and intake.
Intake of vegetables falls short of recommendations to lower risk of chronic diseases. Most research addresses bitterness as a sensory deterrent to consuming vegetables. We examined bitter and sweet sensations from vegetables as mediators of vegetable preference and intake as well as how these tastes vary with markers of genetic variation in taste (3.2 mM 6-n-propylthiouracil bitterness) and taste pathology (1.0 mM quinine bitterness, chorda tympani nerve relative to whole mouth). ⋯ The spatial pattern of quinine bitterness, suggestive of insult to chorda tympani taste fibers, was associated with less bitterness and sweetness from vegetables. Via structural equation modeling, PROP best explained variability in vegetable preference and intake via vegetable bitterness whereas the quinine marker explained variability in vegetable preference and intake via vegetable bitterness and sweetness. In summary, bitterness and sweetness of sampled vegetables varied by taste genetic and taste function markers, which explained differences in preference for vegetables tasted in the laboratory as well as overall vegetable intake outside the laboratory.