Methylglyoxal modification of Nav1.8 facilitates nociceptive neuron firing and causes hyperalgesia in diabetic neuropathy

Time-Course Alterations of Monoamine Levels and Cerebral Blood Flow in Brain Regions after Subarachnoid Hemorrhage in Rats

Pharmacological characterization of different fractions of Calotropis procera (Asclepiadaceae) in streptozotocin induced experimental model of diabetic neuropathy

Cerebral hypoxia has been proposed as a mechanism by which prenatal ethanol exposure causes fetal alcohol spectrum disorder (FASD) in children, but no study had tested this hypothesis using a chronic exposure model that mimicks a common human exposure pattern. Pregnant sheep were exposed to ethanol, 0.75 or 1.75 g kg(-1) (to create blood ethanol concentrations of 85 and 185 mg dl(-1), respectively), or saline 3 days per week in succession (a 'binge drinking' model) from gestational day (GD) 109 until GD 132. Fetuses were instrumented on GD 119-120 and studied on GD 132. The 1.75 g kg(-1) dose resulted in a significant increase in fetal biventricular output (measured by radiolabelled microsphere technique) and heart rate, and a reduction of mean arterial pressure and total peripheral resistance at 1 h, the end of ethanol infusion. The arterial partial pressure of CO(2) was increased, arterial pH was decreased and arterial partial pressure of O(2) did not change. Fetal whole-brain blood flow increased by 37% compared with the control group at 1 h, resulting in increased cerebral oxygen delivery. The elevation in brain blood flow was region specific, occurring preferentially in the ethanol-sensitive cerebellum, increasing by 44% compared with the control group at 1 h. There were no changes in the lower dose group. Assessment of regional differences in the teratogenic effects of ethanol by stereological cell-counting technique showed a reduced number of cerebellar Purkinje cells in response to the 1.75 g kg(-1) dose compared with the control brains. However, no such differences in neuronal numbers were observed in the hippocampus or the olfactory bulb. We conclude that repeated exposure to moderate doses of ethanol during the third trimester alters fetal cerebral vascular function and increases blood flow in brain regions that are vulnerable to ethanol in the presence of acidaemia and hypercapnia, and in the absence of hypoxia.

SUMMARY Regional distribution of brain and myocardial blood flow were examined in 9 instrumented isocapnic normothermic swine, using 15-μm diameter radionuclide-labeled microspheres injected into the left atrium. Minimal alveolar concentration (mac) of halothane required to prevent gross purposeful movement in response to a noxious stimulus in 50% of the pigs was found to be 0.70%. Measurements were made on each animal during nonanesthetized state (control), 1.0 and 1.5 mac halothane anesthesia, and the equivalent of 1.0 and 1.5 mac halothane anesthesia, using 50% N2O. The order of anesthetized steps was randomized for each pig. Recovery periods of 60 minutes were interposed between the anesthetic treatments. During halothane + 50% N2O anesthesia, heart rate, cardiac output, mean aortic pressure, and rate-pressure product were higher than comparable levels of halothane-O2 anesthesia. Halothane caused dose-dependent vasodilatation in all regions of the brain. Cerebral, cerebellar, and brain-stem blood flows at 1.5 mac halothane were 135%, 135%, and 115% of respective control values. Substitution of 50% N2O to maintain same mac dose markedly exaggerated the increment in porcine cerebral and brainstem blood flows, especially at 1.0 mac when perfusions in these regions were 204% and 128% of respective control values. At 1.5 mac anesthesia produced by halothane + 50% N2O, the cerebral, cerebellar, and brain stem perfusions were 153%, 146%, and 129% of control values. Transmural myocardial blood flow decreased from control value with both levels of halothane anesthesia, but with equivalent mac anesthesia produced by halothane + 50% N2O, myocardial perfusion remained near awake values. Subendocardial:subepicardial perfusion ratio remained unchanged from control value throughout the study, indicating that O2 delivery in the inner layers probably kept pace with O2 demand. It is concluded that substitution of 50% N2O for halothane to maintain equipotent anesthesia resulted in a marked increase in regional brain blood flow while myocardial perfusion was maintained near awake values.

Hypercarbia (HC) induced increases in regional brain blood flow (RBBF) may augment regional brain bilirubin deposition (RBBD) in piglets (P). 10 2-4 day old P were infused with bilirubin (BR) to raise & maintain a serum BR of approximately 8 mg/dl. HC (pCO2=76mmHg) was induced with 15% CO2. 14 control (C) P had similar BR levels without HC. Serum free bilirubin was similar in C & HC P. RBBF (by microspheres) & RBBD were as follows:(M±SEM) *p<0.05 vs C, +p<0.05 vs CE value within HC group, CE-cerebrum,TH-thalamus,MB-midbrain,CB-cerebellum,BS-brainstemRBBF was elevated in all regions during HC; the increases in the TH, MB & BS, were greater than for the CE. RBBD was increased following HC in MB & CB; and the increases in MB, CB, & BS were higher than for CE. Regional brain albumin deposition (125I-albumin) was similar in all brain regions. We conclude that deposition of unbound bilirubin in some brain regions is blood flow dependent.

The action of dieldrin on regional brain blood flow in the rat

Summary: We have previously demonstrated regional differences in brain blood flow reduction when hemorrhagic hypotension was induced in spontaneously breathing newborn piglets. Both the mean arterial blood pressure and Paco2 correlated with the changes in brain blood flow. To determine if changes in brain blood flow during hypotension can be attributed to alterations of mean arterial blood pressure alone, eight newborn piglets were studied under conditions of controlled ventilation. Regional brain blood flow was measured by microspheres and the blood pressure was varied by phlebotomy. After baseline determinations, three measurements of blood flow were performed during hypotension. Hypotension produced a significant reduction in blood brain flow confirming the independent effect of mean arterial blood pressure in autoregulation of cerebral circulation. Significantly different regional blood flow responses occurred in response to hypotension (P < 0.05). The % reduction from control blood flow was greatest to the cerebrum, less to the cerebellum, and least to the brainstem. Furthermore, the blood flow was consistently decreased in the cerebral hemispheres during the entire exposure to hypotension (mean ± S.E.: −36 ± 10%, −18 ± 11%, and −33 ± 11% change from control) whereas the brainstem demonstrated an intial reduction and then an increase in blood flow (mean ± SE: −14 ± 12%, +16 ± 15%, and +5.5 ± 13% change from control). The cerebellar responses were intermediate between those of the cerebrum and brainstem. O2 delivery was significantly decreased to all brain regions during hypotension, maintaining the same rank order of the regions as when blood flow reductions occurred. Speculation: Newborn piglets subjected to profound hypotension demonstrate regional differences in the reduction of brain blood flow. Cranial window studies of the microvasculature in adult cats clearly demonstrate that precapillary vessels in the brain do not respond in an identical manner to hypotension but rather react in a size dependent fashion. The observed differences in brain regional blood flow are possibly a manifestation of the relative composition (with respect to vessel size) of the regional parenchymal arterial beds.

Although many people who use tanning beds are aware of the negative consequences, they continue to indoor tan, possibly due to addictive properties. The purpose of this paper is to review the existing literature on tanning addiction, its potential biological mechanisms, and its association with psychological disorders. A PubMed search was conducted using the terms "Tanning Addiction," "UVR AND B-endorphin," and "tanning dependence AND gene." The articles were organized based on the following categories: endorphins, dopamine and the brain, genetic associations, and associations between tanning addiction and other disorders. Exposure to ultraviolet radiation leads to the synthesis of β-endorphins in the skin, the release of dopamine in the brain, and increased blood flow in brain regions associated with reinforcement and addiction. Genes associated with tanning addiction include PTCHD2 and ANKK1. Several psychiatric disorders are comorbidities of tanning addiction and excessive indoor tanning parallels many of the patterns of substance use disorders. In frequent indoor tanners, greater awareness of tanning's addictive potential and further development of interventions aimed at treating this addictive behaviour may be needed to stop indoor tanning.

Studies of proteolytic enzymes (proteinases) like thrombin and trypsin have long been the province of cardiovascular and gastrointestinal physiologists: thrombin as the key regulator of the coagulation cascade and trypsin and other pancreatic enzymes as the means for breaking down proteins in the small intestine. Conforming to a long-standing pattern of ‘where GI physiologists tread, neuroscientists inevitably follow’, the identification of proteinase-activated receptors (PARs) on peripheral and central neurones has generated increasing interest in how they may function in the nervous system (Noorbakhsh et al. 2003; Ossovskaya & Bunnett, 2004). PARs are a four-membered family of G-protein coupled receptors (PAR1–4) whose activation by serine proteinases occurs by enzymatic cleavage at N-terminal serines to expose a ‘tethered ligand’ that binds residues in its own second extracellular domain to initiate signal transduction (Ossovskaya & Bunnett, 2004). PAR-2 has become the current favourite as a promising target in anti-inflammatory/chronic pain drug discovery programmes because it is expressed in sensory nociceptive neurones, its activation releases peptides (SP/CGRP) from afferent nerve endings in the dorsal horn and results in both thermal and mechanical hyperalgesia, and it can be activated by tryptase, which is secreted by mast cells onto adjacent neurones under inflammatory conditions or neuronal damage (Noorbakhsh et al. 2003; Ossovskaya & Bunnett, 2004). Because it is the only PAR not activated by thrombin, selective blockade of this receptor could be therapeutically useful in pain management without antithrombotic side-effects. How does PAR-2 signalling lead to thermal and mechanical hyperalgesia? A global network of research groups, headed by Nigel Bunnett, have presented a set of tour de force studies showing that PAR-2 activates multiple second messenger pathways to sensitize TRPV1 and TRPV4 receptors on nociceptive neurones and this, in turn, releases nociceptive peptides (SP and CGRP) onto centrally projecting nociceptors that can account for TRPV1-dependent thermal and TRPV4-dependent mechanical hyperalgesia (Amadesi et al. 2006; Grant et al. 2007). TRPV1 and TRPV4 receptors are calcium-permeable cationic ion channels activated by multiple sensory stimuli; of relevance here is that TRPV1 can be gated by noxious heat (> 42°C) and capsaicin, and TRPV4 by warm temperature (> 27°C), hypotonicity and shear stress (Nilius et al. 2004). Amadesi et al. (2006) found that PAR-2 colocalized with protein kinase (PK) Ce, and PKA in a subset of TRPV1-containing dorsal root neurones, that PAR-2 agonists activated these pathways, increased TRPV1-mediated calcium influx and whole-cell currents and caused thermal hyperalgesia in mice. Moreover, inhibition of PKCe and PKA prevented the PAR-2 sensitization of TRPV1 calcium transients and currents as well as PAR-2-induced thermal hyperalgesia in mice. Grant et al. (2007) found that PAR-2 also colocalized with TRPV4, SP and CGRP in dorsal root ganglia, that PAR-2 agonists enhanced TRPV4-induced calcium transients and whole-cell currents and that inhibition of phospholipase Cβ, PKA, PKC and PKD prevented the PAR-2-induced sensitization of TRPV4-induced responses. They also found that activation of TRPV4 stimulated the release of SP and CGRP from dorsal horn neurones and this release was potentiated by PAR-2 activation, similar to their previously demonstrated PAR-2 enhancement of TRPV1 release of SP and CGRP (Amadesi et al. 2004). Intraplantar injection of PAR-2 agonists caused mechanical hyperalgesia as well as sensitized pain responses to TRPV4 activation in wild-type but not in TRPV4-deleted mice. These findings provided the basis for a model outlined by Grant et al. (2007) to account for protease-induced mechanical hyperalgesia, a model that can also apply to protease-induced thermal hyperalgesia. Proteases are released in response to inflammatory stimuli where they can activate PAR-2 on nociceptive afferent nerve endings in peripheral tissue. PAR-2 couples to activation of multiple second messenger kinases (PKA, PKC, PKD) in these nerve endings to sensitize TRPV1 and TRPV4 receptors. Sensitized TRPV1 receptors now respond to non-noxious temperature while sensitized TRPV4 receptors show enhanced response to mechanical stimuli; in both cases their increased gating results in increased release of SP and CGRP from dorsal horn terminals with consequent increased transmission centrally. In terms of pathological pain states, prevention of TRPV1 and TRPV4 receptor sensitization is a more attractive therapeutic aim than inhibition of TRPV receptors per se. In this regard, it is of interest to compare results from a recent study by Alessandri-Haber et al. (2006) who found similar mechanisms of TRPV4-dependent sensitization and mechanical hyperalgesia in response to a cocktail of inflammatory mediators (bradykinin, SP, 5-HT, histamine and prostaglandin), none of which alone was sufficient to engage TRPV4-dependent hyperalgesia. PAR-2 antagonists may well pack more punch against neuropathic or inflammatory pain.

To determine the limits of aortic blood pressure in infant lambs for autoregulation of global and regional brain blood flow, we studied 10 unsedated lambs during hypotension and 10 unsedated lambs during hypertension. In lambs 6 to 13 d old, we produced graded changes in aortic blood pressure by inflating a balloon occluder placed around either the inferior vena cava or the descending aorta. Using radiolabeled microspheres, we measured global and regional brain blood flow at the baseline, and then with each graded change in aortic blood pressure. In an additional step, we administered atropine to determine if its antimuscarinic properties alter the fall in brain blood flow with severe hypotension, or alter the rise in brain blood flow with severe hypertension. We concluded that in the unsedated infant lamb, global brain blood flow remains stable between mean aortic blood pressures of 6.0 to 10.0 kPa (45 to 82 torr), a range from approximately 38% below to 12% above normal mean aortic blood pressure. We noted that this autoregulatory range is essentially unchanged from that described for the fetal lamb at 80% of term gestation--even though the mean aortic blood pressure rises during this period of maturation by more than 2.7 kPa (20 torr). We found that the lower limit of autoregulation varies among the different brain regions and is lowest in the thalamus, pons, and medulla. We saw little variation of the upper limit among the brain regions. Finally, we determined that atropine does not alter brain blood flow during severe hypotension or severe hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

BackgroundNeuroimaging studies have yielded significant advances in the understanding of neural processes relevant to the development and persistence of addiction. However, these advances have not explored extensively for diagnostic accuracy in human subjects. The aim of this study was to develop a statistical approach, using a machine learning framework, to correctly classify brain images of cocaine-dependent participants and healthy controls. In this study, a framework suitable for educing potential brain regions that differed between the two groups was developed and implemented. Single Photon Emission Computerized Tomography (SPECT) images obtained during rest or a saline infusion in three cohorts of 2–4 week abstinent cocaine-dependent participants (n = 93) and healthy controls (n = 69) were used to develop a classification model. An information theoretic-based feature selection algorithm was first conducted to reduce the number of voxels. A density-based clustering algorithm was then used to form spatially connected voxel clouds in three-dimensional space. A statistical classifier, Support Vectors Machine (SVM), was then used for participant classification. Statistically insignificant voxels of spatially connected brain regions were removed iteratively and classification accuracy was reported through the iterations.ResultsThe voxel-based analysis identified 1,500 spatially connected voxels in 30 distinct clusters after a grid search in SVM parameters. Participants were successfully classified with 0.88 and 0.89 F-measure accuracies in 10-fold cross validation (10xCV) and leave-one-out (LOO) approaches, respectively. Sensitivity and specificity were 0.90 and 0.89 for LOO; 0.83 and 0.83 for 10xCV. Many of the 30 selected clusters are highly relevant to the addictive process, including regions relevant to cognitive control, default mode network related self-referential thought, behavioral inhibition, and contextual memories. Relative hyperactivity and hypoactivity of regional cerebral blood flow in brain regions in cocaine-dependent participants are presented with corresponding level of significance.ConclusionsThe SVM-based approach successfully classified cocaine-dependent and healthy control participants using voxels selected with information theoretic-based and statistical methods from participants’ SPECT data. The regions found in this study align with brain regions reported in the literature. These findings support the future use of brain imaging and SVM-based classifier in the diagnosis of substance use disorders and furthering an understanding of their underlying pathology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-016-1218-z) contains supplementary material, which is available to authorized users.

Since kernicteric lesions are usually found in the subcortical regions of the brain and these areas also receive the highest blood flow during asphyxia and hypercapnia, we hypothesized that increases in brain bilirubin deposition may be related to increases in brain blood flow. Fourteen piglets underwent a 3-h infusion of bilirubin to maintain total serum bilirubin at approximately 8 mg/dl, during which time blood gases, hemodynamic variables, and brain blood flow were determined. After sacrificing the animals, regional brain bilirubin content was determined. Ten piglets underwent the same protocol; in addition, hypercapnia was induced during the last hour of study (PaCO2 approximately 70 mm Hg). The regional brain blood flow and bilirubin deposition were significantly increased over control values (p less than 0.05) following hypercapnia in the subcortical region and significantly so in the midbrain and cerebellum. In separate groups of control (n = 6) and hypercapnia (n = 6) piglets, 125I-labeled albumin was infused and demonstrated that hypercapnia was not associated with increased regional brain albumin content. We conclude that hypercapnia-induced augmentation in regional brain blood flow is associated with increased deposition brain blood flow is associated with increased deposition of unbound bilirubin. Although the causal relationship between these two observations has not been firmly established, the findings deserve future investigation to clarify the role of brain blood flow, brain bilirubin deposition, and the production of kernicterus in high risk infants.

Changes in regional brain blood flow and hemoglobin oxygen saturation occur in the human cortex in response to neural activation. These changes create a signal that can be imaged and quantitated using various methods, most of which do not allow for continuous bedside measurements. Imaging methods using near-infrared light, however, have been described. These allow for non-invasive measurements, and take advantage of the fact that hemoglobin is a strong absorber at these wavelengths and thus acts as a naturalÓ contrast agent. We have generated brain functional images of ill, premature infants during passive movement of the forearm using the Boston Diffusion Optical Tomography System (DOTS), a system which allows for near real-time bedside assessments. For these initial feasibility studies in the neonatal intensive care unit (NICU), custom-made soft flexible probes were made, and passive motor tasks were performed during imaging. We found that specific passive movements of the arm resulted in focal, reproducible changes in cerebral absorption at 830 nm, indicating an increase in regional blood flow and oxygenation. Further bedside studies have since been undertaken using 780 nm and 830 nm lasers. These studies indicate that the Boston DOTS is a safe and feasible bedside near-infrared functional imaging device, and underline the importance offurther studies in this critically ill patient group at high risk for brain injury.

Low-Dose Poly(ADP-Ribose) Polymerase Inhibitor-Containing Combination Therapies Reverse Early Peripheral Diabetic Neuropathy

&lt;p&gt;The complement system is a principal component of innate immunity. Recent studies have underscored the importance of C5a and other complement components in inflammatory and neuropathic pain, although the underlying mechanisms are largely unknown. In particular, it is unclear how the complement system communicates with nociceptors and which ion channels and receptors are involved. Here we demonstrate that inflammatory thermal and mechanical hyperalgesia induced by complete Freund’s adjuvant were accompanied by C5a upregulation and were markedly reduced by C5a receptor (C5aR1) knockout (KO) or treatment with the C5aR1 antagonist PMX53. Direct administration of C5a into the mouse hindpaw produced strong thermal and mechanical hyperalgesia, an effect that was absent in TRPV1 KO mice, and was blocked by the TRPV1 antagonist AMG9810. Immunohistochemistry of mouse plantar skin showed prominent expression of C5aR1 in macrophages. Additionally, C5a evoked strong Ca2+ mobilization in macrophages. Macrophage depletion in transgenic macrophage Fas-induced apoptosis (MAFIA) mice abolished C5a-dependent thermal and mechanical hyperalgesia. Examination of inflammatory mediators following C5a injection revealed a rapid upregulation of nerve growth factor (NGF), a mediator known to sensitize TRPV1. Pre-injection of an NGF-neutralizing antibody or Trk inhibitor GNF-5837 prevented C5a-induced thermal hyperalgesia. Notably, NGF-induced thermal hyperalgesia was unaffected by macrophage depletion. Collectively, these results suggest that C5a induces thermal and mechanical hyperalgesia by triggering macrophage-dependent signaling that involves mobilization of NGF and NGF-dependent sensitization of TRPV1. Our findings highlight the importance of macrophage-to-neuron signaling in pain processing and identify C5a, NGF and TRPV1 as key players in this cross-cellular communication.&lt;/p&gt;