Physiology & behavior
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Physiology & behavior · Dec 2010
Progesterone rapidly recruits female-typical opioid-induced hyperalgesic mechanisms.
Continuous morphine treatment can paradoxically increase nociception (i.e. hyperalgesia) in male and female mice, but sex differences have been reported. Here, we studied progesterone modulation of these differences by assessing nociception on the tail-withdrawal test in male and female mice rendered hyperalgesic during continuous infusion of two different morphine doses (1.6 and 40.0mg/kg/24h). Although the lower morphine infusion dose increased nociception in both sexes by infusion Day 4, this hyperalgesia dissipated by Day 6 in males and ovariectomized females, but not gonadally intact females. ⋯ However, the NMDA receptor antagonist MK-801 (0.05mg/kg) reversed hyperalgesia in males and ovariectomized females but not gonadally intact females on infusion Day 6. Subcutaneous progesterone (0.0016mg/kg) injection inhibited this reversal in male and ovariectomized female mice but had no effect on nociception in saline-infused mice of either sex. These data confirm our previous findings that male and female mice utilize distinct hyperalgesic mechanisms, and show for the first time that a single progesterone bolus dose can recruit female-typical hyperalgesia in ovariectomized females and males.
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Physiology & behavior · Nov 2010
Comparative StudyRole of melanin-concentrating hormone in the control of ethanol consumption: Region-specific effects revealed by expression and injection studies.
The peptide melanin-concentrating hormone (MCH), produced mainly by cells in the lateral hypothalamus (LH), perifornical area (PF) and zona incerta (ZI), is suggested to have a role in the consumption of rewarding substances, such as ethanol, sucrose and palatable food. However, there is limited information on the specific brain sites where MCH acts to stimulate intake of these rewarding substances and on the feedback effects that their consumption has on the expression of endogenous MCH. The current study investigated MCH in relation to ethanol consumption, in Sprague-Dawley rats. ⋯ In contrast, it reduced ethanol intake when administered into the LH, while having no effect in the ZI. These results demonstrate that voluntary, chronic consumption of ethanol leads to local negative feedback control of MCH expression in the LH. However, with a brief exposure, ethanol stimulates MCH-expressing neurons in this region, which through projections to the feeding-related PVN and reward-related NAc can promote further drinking behavior.
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Physiology & behavior · Nov 2010
Comparative StudyRole of caloric homeostasis and reward in alcohol intake in Syrian golden hamsters.
The Syrian golden hamster drinks alcohol readily, but only achieves moderate blood alcohol levels, and does not go through withdrawal from alcohol. Because the hamster is a model of caloric homeostasis, both caloric content and reward value may contribute to the hamster's alcohol consumption. The current study examines alcohol consumption in the hamster when a caloric or non-caloric sweet solution is concurrently available and caloric intake in the hamster before, during, and after exposure to either: alcohol, sucrose or saccharin. ⋯ Exposure to sucrose and alcohol but not saccharin decreased food intake. Decreased alcohol consumption in response to a caloric sweetener and decreased food intake during alcohol exposure support that alcohol consumption by the hamster is mediated by caloric content. However, suppression of alcohol intake by a sucrose solution of lower caloric content and the equivalent intake of individual alcohol, sucrose and saccharin solutions support a role for reward value in alcohol consumption.
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Physiology & behavior · Aug 2010
Comparative StudyTake a deep breath: the relief effect of spontaneous and instructed sighs.
Spontaneous sighing is related to subjective relief of negative emotional states. Whether this also applies to instructed sighing is not known. The present study aimed to investigate sEMG and respiratory variability (1) during recovery from mental stress with and without an instructed sigh; (2) before and after spontaneous sighs throughout the experiment. ⋯ Following an instructed sigh, a smaller reduction in sEMG and an increase in random respiratory variability during recovery from mental stress were observed. Thus, a spontaneous sigh seemed to induce relief. An instructed sigh appeared to inhibit recovery from mental stress.
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Physiology & behavior · Aug 2010
Comparative StudyAnxiety and stress can predict pain perception following a cognitive stress.
Hoeger Bement, M. K., A. Weyer, M. ⋯ The increase-pain group (n=8) had lower baseline stress and anxiety, lower baseline pain reports, and large anxiety response following the mental math. In contrast, the decrease-pain group (n=9) had higher baseline stress and anxiety levels, higher baseline pain reports, and a large increase in cortisol levels. Thus, the differential response in the changes in pain perception was related to anxiety and stress levels prior to and during the cognitive stressor, indicating that psychosocial characteristics can help determine the stress-induced pain response.