Brain research bulletin
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Brain research bulletin · Aug 2010
Effects of neonatal inflammation on descending modulation from the rostroventromedial medulla.
Cutaneous tissue inflammation during the first postnatal week is known to alter long-term development of spinal cord nociceptive circuitry and to alter behavioral responses to noxious stimuli in adult animals. The impact of neonatal inflammation on descending projections arising from supraspinal sites that modulate spinal nociceptive processing is unknown. In the present study, we investigated if altered behavioral responses to pain in adult animals after neonatal inflammation are associated with changes in descending modulation of nocifensive responses elicited from the rostroventromedial medulla (RVM) in lightly anesthetized rats. ⋯ No differences in the efficacy of RVM stimulation between CG and control animals were observed 24h after reinflammation with CFA. These findings indicate that neonatal tissue injury and inflammation produces lasting alterations in descending modulatory systems that modify nociceptive processing. Taken together with previous studies, these results indicate that changes in pain sensitivity following neonatal tissue injury involve long-term alterations in spinal and supraspinal circuitry.
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Brain research bulletin · Jul 2010
Protective effects of trans-2, 4-dimethoxystibene on cognitive, impairments induced by Abeta(25-35) in, hypercholesterolemic rats.
Trans-2, 4-dimethoxystibene (S3) is a synthetic stilbenes. In the present study, S3 was investigated to assess its neuroprotective effect against the toxicity induced by Abeta(25-35) in hypercholesterolemic rats. Rats were fed with hypercholesterolemic chow for six weeks, and then received a single intracerebroventricular (i.c.v.) injection of Abeta(25-35) and a treatment with S3 or estradiol (E2). ⋯ The data showed that consumption of S3 (50mg/kg/d) significantly ameliorated the cognitive deficits and neuron apoptosis caused by i.c.v. injection of Abeta(25-35). Meanwhile, S3 reversed the decreased activity of ChAT, SOD, GSH-Px and contents of Ach, as well as the increased activity of AchE, MDA contents and the release of cytochrome C in hippocampus. These findings suggest that S3 may be a potential candidate for development as therapeutic agent to treat AD through regulating cholinergic nerve system and anti-oxidative mechanism.
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Brain research bulletin · May 2010
Opioidergic and GABAergic mechanisms in the rostral ventromedial medulla modulate the nociceptive response of vocalization in guinea pigs.
Vocalization generated by the application of a noxious stimulus is an integrative response related to the affective-motivational component of pain. The rostral ventromedial medulla (RVM) plays an important role in descending pain modulation, and opiates play a major role in modulation of the antinociception mediated by the RVM. Further, it has been suggested that morphine mediates antinociception indirectly, by inhibition of tonically active GABAergic neurons. ⋯ These observations suggest an antinociceptive and pro-nociceptive role of the opioidergic and GABAergic neurotransmitters in the RVM, respectively. Our data show that opioids have an antinociceptive effect in the RVM, while GABAergic neurotransmission is related to the facilitation of nociceptive responses. Additionally, our results indicate that the antinociceptive effect of the opioids in the RVM could be mediated by a disinhibition of tonically active GABAergic interneurons in the downstream projection neurons of the descending pain control system; indicating an interaction between the opioidergic and GABAergic pathways of pain modulation.
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Brain research bulletin · Apr 2010
Increased sensitivity to supra-threshold painful stimuli in patients with multiple functional somatic symptoms (MFS).
Many patients in a variety of medical settings suffer from persistently painful bodily symptoms that are not explained by known pathophysiological mechanisms. In the most severe cases, these patients complain of multiple functional somatic symptoms (MFS). We tested the hypothesis of reduced pain threshold and pain tolerance levels in patients with MFS. ⋯ Pain tolerance scores were identical in the two groups but they correlated negatively with the number of functional somatic symptoms in MFS patients. Importantly, patients had a smaller temperature range between their pain threshold and pain tolerance scores, suggesting that they differentiate poorly within the noxious range. Minor increases in stimulus intensity of supra-threshold painful stimuli may lead to disproportionate increases in pain intensity in MFS patients, suggesting a defunct endogenous pain modulatory system.
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Brain research bulletin · Apr 2010
Cardiovascular and respiratory correlates of deep nociceptive stimulation, suggestions for analgesia, pain imagery and cognitive load as a function of hypnotizability.
Hypnotizability is a cognitive trait modulating some physiological responses to cognitive and physical stimulation also in the normal awake state and in the absence of specific suggestions. Aim of the study was the characterization of the cardiovascular correlates of deep pain induced by nociceptive pressor stimulation without (PAIN) and with (AN) suggestions for analgesia, pain imagery/perception (IM) and mental computation (MC) in not hypnotized highly (Highs) and low (Lows) hypnotizable healthy subjects of both genders. The subjective experience of pain intensity, relaxation and task related fatigue were measured through a structured interview. ⋯ On the whole, the haemodynamic response consisted of decreased systolic/mean blood pressure and maximum skin blood flow together with increased diastolic blood pressure/minimum skin blood flow in both groups during all conditions. Scarce differences were observed between Highs and Lows (in systolic blood pressure during IM and in respiratory amplitude during PAIN, AN and IM, modulated by gender). The results indicate that in not hypnotized subjects hypnotizability is not associated with relevant differences in the autonomic responses to deep pain, suggestions for analgesia, pain imagery/perception and cognitive load.