Physiology & behavior
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Physiology & behavior · Mar 2000
Clinical Trial Controlled Clinical TrialPsychophysiological stress responses in amputees with and without phantom limb pain.
The present experiment tested the hypothesis that phantom limb pain amputees show a different pattern of psychophysiological reactivity to stress compared with painfree amputees. Six phantom limb pain (PLP) and five painfree upper-extremity amputees were administered two groups of tasks: stressful and relaxing. The measured dependent variables were skin temperature recorded at both stump and intact site, heart rate, blood pressure, subjective pain and stress ratings. ⋯ Results indicate that peripheral factors, such as stump temperature reliably differentiate PLP from painfree patients. Moreover, the clear cardiovascular hyperreactivity observed in PLP patients during their report of amputation suggests that PLP is associated with a long-term emotional memory for the painful experience of that event. These results are consistent with most reports in the literature relating phantom pain development to the experience of preamputation pain.
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Physiology & behavior · Feb 2000
Environmental stress modifies glycemic control and diabetes onset in type 2 diabetes prone Otsuka Long Evans Tokushima Fatty (OLETF) rats.
This study was designed to investigate the effects of environmental stress on metabolic derangements and the expression of diabetes phenotype in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of human type 2 diabetes (NIDDM). Acute environmental stress, i.e., exposure to water with immobilization for 1 h, caused a transient increase in blood glucose with decreased insulin secretion, and the stress-induced hyperglycemia augmented with age. The increased glycemia was associated with increased plasma levels of catecholamines and corticosterone. ⋯ These results suggest that chronic stress from 8 weeks of age inhibited weight gain, probably due to changes in eating behavior, preventing the deterioration of insulin resistance in OLETF rats. Plasma leptin levels were not modulated by stress, and correlated with body weight in the rats under chronic stress and in controls. These results suggest that in type 2 diabetes, blood glucose derangement due to stress is presumably associated not only with changes in counterregulatory hormones involved in glucose metabolism, but also with stress-induced changes in eating behavior.
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Physiology & behavior · Aug 1999
Comparative StudyComparison of the effects of a high-fat and high-carbohydrate soup delivered orally and intragastrically on gastric emptying, appetite, and eating behaviour.
To investigate the effects of fat and carbohydrate on appetite, food intake and gastric emptying with and without the influence of orosensory factors, a group of nine healthy, fasted male subjects took part in two separate paired experiments involving high-fat and high-carbohydrate radiolabelled soup preloads. In the first experiment subjects received direct intragastric isocaloric infusions of either a high-fat tomato soup or a high-carbohydrate tomato soup (400 kcal in 425 mL) over 15 min, on two occasions. In the second paired experiment subjects ingested the same high-fat and high-carbohydrate soup over 15 min. ⋯ When soup was administered intragastrically (Experiment 1) both the high-fat and high-carbohydrate soup preloads suppressed appetite ratings from baseline, but there were no differences in ratings of hunger and fullness, food intake from the test meal, or rate of gastric emptying between the two soup preloads. When the same soups were ingested (Experiment 2), the high-fat soup suppressed hunger, induced fullness, and slowed gastric emptying more than the high-carbohydrate soup and also tended to be more effective at reducing energy intake from the test meal. The results of these studies demonstrate that orosensory stimulation plays an important role in appetite regulation, and also indicate that subtle differences in orosensory stimulation produced by particular nutrients may profoundly influence appetite and gastrointestinal responses.
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Physiology & behavior · Jan 1999
Clinical TrialAn examination of the effects of isoenergetic intragastric infusions of pure macronutrients on cold pain perception in healthy human volunteers.
Our previous study demonstrated that meals, particularly when rich in fat, significantly reduced the pain induced by the cold pressor stimulus in healthy human subjects. To determine the mechanisms involved, the aim of this study was to bypass the taste and cognitive component of food and to investigate the scope of these analgesic effects with direct intragastric infusion of pure macronutrients in a group of 16 healthy human volunteers (eight male and eight female) on the response to cold-induced pain. All subjects underwent the cold pressor test (CPT) on three occasions in a counterbalanced order: before and after intragastric intubation and infusion of isoenergetic fat (10% intralipid), carbohydrate (CHO-maltodextrin), and a control infusion of isotonic saline. ⋯ The CPT was carried out four times on each test day, once before intubation, and 0.5, 1.5, and 2.5 h after intragastric infusion. Radial pulse and blood pressure measurements and visual analogue scales of mood/emotional state were carried out before and after each CPT. There were no significant differences in pain scores between the three test conditions, suggesting that by bypassing the cognitive and taste component of eating, the trigger for any postingestive analgesic effects of food are lost.
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Physiology & behavior · Jan 1999
Unilateral block of NMDA receptors in the amygdala prevents predator stress-induced lasting increases in anxiety-like behavior and unconditioned startle--effective hemisphere depends on the behavior.
Lasting increases in anxiety-like behavior (ALB) in the elevated plus-maze are produced by a single 5-min exposure of a rat to a cat. Rats become more anxious in the plus-maze for up to 3 weeks after the exposure. The first study in this series demonstrated that blockade of NMDA receptors in rats with MK-801, AP7, or CPP, given systemically 30 min prior to exposure to a cat prevents the increase in ALB assessed 1 week later in the elevated plus-maze. ⋯ The data also suggest that the right amygdala action is "downstream" from the left amygdala contribution. These findings are consistent with the view that NMDA receptors are involved in initiation, but not maintenance, of neural changes mediating lasting increases in anxiety following severe stress. Finally, the findings of the importance of the right amygdala in stress-induced enhancement of the startle response provides neurobiological face validity to predator stress as a model of aspects of posttraumatic stress disorder.