Physiology & behavior
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Physiology & behavior · May 2014
Acid-induced hyperalgesia and anxio-depressive comorbidity in rats.
Fibromyalgia is a prevalent disorder characterized by chronic widespread pain (CWP) and complex comorbid symptoms. A CWP model is developed through repeated unilateral intramuscular injections of acid saline resulting in bilateral mechanical hyperalgesia in rats. The present study aims to evaluate whether both anxious and depressive comorbidities exist in this acid-induced pain model, similarly to patients with CWP syndromes. ⋯ Moreover, rats with chronic pain showed significantly longer immobility than the vehicle group in the forced swimming test. The results indicate that psychiatric behaviors are exacerbated in the CWP model. This study provides evidence for the validity of the acid-induced pain model analogous to patients with CWP syndromes.
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Possible interactions of melatonin with concurrently administered drugs were investigated in in vitro studies utilising human hepatic post-mitochondrial preparations; similar studies were conducted with rat preparations to ascertain whether rat is a suitable surrogate for human. Drugs were selected based not only on the knowledge that the 6-hydroxylation of exogenous melatonin, its principal pathway of metabolism, is mainly mediated by hepatic CYP1A2, but also on the likelihood of the drug being concurrently administered with melatonin. ⋯ Of the drugs screened, only the potent CYP1A2 inhibitor 5-methoxypsoralen impaired the 6-melatonin hydroxylation at pharmacologically relevant concentrations, and is likely to lead to clinical interactions; diazepam, tamoxifen and acetaminophen (paracetamol) did not impair the metabolic conversion of melatonin to 6-sulphatoxymelatonin at concentrations attained following therapeutic administration. 17-Ethinhyloestradiol appeared not to suppress the 6-hydroxylation of melatonin but inhibited the sulphation of 6-hydroxymelatonin, but this is unlikely to result in an interaction following therapeutic intake of the steroid. Species differences in the inhibition of melatonin metabolism in human and rat hepatic post-mitochondrial preparations were evident implying that the rat may not be an appropriate surrogate of human in such studies.
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Physiology & behavior · May 2014
If it makes you feel bad, don't do it! Egoistic rather than altruistic empathy modulates neural and behavioral responses in moral dilemmas.
According to Greene et al.'s dual-process theory, the differential involvement of emotional processes would explain the different patterns of moral judgments people typically produce when faced with Trolley- and Footbridge-type dilemmas. As a relevant factor, dispositional empathy is known to motivate prosocial behaviors, thus playing a central role in moral judgment and behavior. The present study was aimed at investigating how behavioral and neural correlates of moral decision-making are modulated by the cognitive and affective dimensions of empathy. ⋯ Scores on the Empathic Concern affective subscale of the IRI positively predicted unpleasantness experienced during decision-making for all dilemmas. On the other hand, for Footbridge-type dilemmas only, scores on the Personal Distress affective subscale predicted negatively the mean percentages of utilitarian choices and positively the mean amplitudes of the P260, an ERP component reflecting an immediate emotional reaction during decision-making. It is concluded that "self-oriented" feelings of anxiety and unease, rather than "other-oriented" feelings of concern, affect behavioral choices and emotion-related cortical activity in Footbridge-type moral dilemmas.
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Physiology & behavior · May 2014
C-Fos activation in the periaqueductal gray following acute morphine-3β-D-glucuronide or morphine administration.
Morphine-3β-D-glucuronide (M3G), a primary morphine metabolite, evokes hyperalgesia in mice and rats and putatively mediates hyperalgesia associated with morphine (MOR) administration. However, M3G does not act via opioid receptors and its locus of activity in the CNS is unknown. Here we assessed the density of neurons immunoreactive for c-Fos, an immediate early gene regulated by neuronal activity, in the periaqueductal gray (PAG), a midbrain region critical to pain modulation, in male CD-1 mice after MOR and M3G exposure. ⋯ However, NTX pre-injection blocked this increase in MOR but not M3G injected mice. The data demonstrate for the first time a CNS locus for M3G activity. Consistent with previous observations, this M3G activity is not mediated by opioid receptors.
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Physiology & behavior · May 2014
Effects of energy status and diet on Bdnf expression in the ventromedial hypothalamus of male and female rats.
Sex differences exist in the regulation of energy homeostasis in response to calorie scarcity or excess. Brain-derived neurotrophic factor (BDNF) is one of the anorexigenic neuropeptides regulating energy homeostasis. Expression of Bdnf mRNA in the ventromedial nucleus of the hypothalamus (VMH) is closely associated with energy and reproductive status. ⋯ Decreased BDNF signaling during HFD feeding would increase a drive to eat and may contribute to diet-induced obesity in males. In contrast, VMH Bdnf expression was stably maintained in females when energy homeostasis was disturbed. These results suggest sex-distinct regulation of central Bdnf expression by diet and energy status.