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Gastrointestinal (GI) discomfort is a hallmark of most gut disorders and represents an important component of chronic visceral pain1. For the growing population afflicted by irritable bowel syndrome, GI hypersensitivity and pain persist long after tissue injury has resolved2. Irritable bowel syndrome also exhibits a strong sex bias, afflicting women three times more than men1. Here, we focus on enterochromaffin (EC) cells, which are rare excitable, serotonergic neuroendocrine cells in the gut epithelium3–5. EC cells detect and transduce noxious stimuli to nearby mucosal nerve endings3,6 but involvement of this signalling pathway in visceral pain and attendant sex differences has not been assessed. By enhancing or suppressing EC cell function in vivo, we show that these cells are sufficient to elicit hypersensitivity to gut distension and necessary for the sensitizing actions of isovalerate, a bacterial short-chain fatty acid associated with GI inflammation7,8. Remarkably, prolonged EC cell activation produced persistent visceral hypersensitivity, even in the absence of an instigating inflammatory episode. Furthermore, perturbing EC cell activity promoted anxiety-like behaviours which normalized after blockade of serotonergic signalling. Sex differences were noted across a range of paradigms, indicating that the EC cell–mucosal afferent circuit is tonically engaged in females. Our findings validate a critical role for EC cell–mucosal afferent signalling in acute and persistent GI pain, in addition to highlighting genetic models for studying visceral hypersensitivity and the sex bias of gut pain.Visceral pain and anxiety in mice are found to be associated with gut enterochromaffin cells, and genetic models for eliciting visceral hypersensitivity and studying the sex bias of gut pain are proposed. [ABSTRACT FROM AUTHOR]

Our understanding of how abdominal organs (like the gut) communicate with the brain, via sensory nerves, has been limited by a lack of techniques to selectively activate or inhibit populations of spinal primary afferent neurons within dorsal root ganglia (DRG), of live animals. We report a survival surgery technique in mice, where select DRG are surgically removed (unilaterally or bilaterally), without interfering with other sensory or motor nerves. Using this approach, pain responses evoked by rectal distension were abolished by bilateral lumbosacral L5-S1 DRG removal, but not thoracolumbar T13-L1 DRG removal. However, animals lacking T13-L1 or L5-S1 DRG both showed reduced pain sensitivity to distal colonic distension. Removal of DRG led to selective loss of peripheral CGRP-expressing spinal afferent axons innervating visceral organs, arising from discrete spinal segments. This method thus allows spinal segment-specific determination of sensory pathway functions in conscious, free-to-move animals, without genetic modification. A surgical method in mice can selectively remove dorsal root ganglia (DRG) at specific spinal levels without interfering with other nerves, providing insight on thoracolumbar vs. lumbosacral DRG contributions to pain signalling and behaviour. [ABSTRACT FROM AUTHOR]

The mechanisms underlying chronic bladder conditions such as interstitial cystitis/bladder pain syndrome (IC/BPS) and overactive bladder syndrome (OAB) are incompletely understood. However, targeting specific receptors mediating neuronal sensitivity to specific stimuli is an emerging treatment strategy. Recently, irritant-sensing receptors including the bile acid receptor TGR5, have been identified within the viscera and are thought to play a key role in neuronal hypersensitivity. Here, in mice, we identify mRNA expression of TGR5 (Gpbar1) in all layers of the bladder as well as in the lumbosacral dorsal root ganglia (DRG) and in isolated bladder-innervating DRG neurons. In bladder-innervating DRG neurons Gpbar1 mRNA was 100% co-expressed with Trpv1 and 30% co-expressed with Trpa1. In vitro live-cell calcium imaging of bladder-innervating DRG neurons showed direct activation of a sub-population of bladder-innervating DRG neurons with the synthetic TGR5 agonist CCDC, which was diminished in Trpv1−/− but not Trpa1−/− DRG neurons. CCDC also activated a small percentage of non-neuronal cells. Using an ex vivo mouse bladder afferent recording preparation we show intravesical application of endogenous (5α-pregnan-3β-ol-20-one sulphate, Pg5α) and synthetic (CCDC) TGR5 agonists enhanced afferent mechanosensitivity to bladder distension. Correspondingly, in vivo intravesical administration of CCDC increased the number of spinal dorsal horn neurons that were activated by bladder distension. The enhanced mechanosensitivity induced by CCDC ex vivo and in vivo was absent using Gpbar1−/− mice. Together, these results indicate a role for the TGR5 receptor in mediating bladder afferent hypersensitivity to distension and thus may be important to the symptoms associated with IC/BPS and OAB. [ABSTRACT FROM AUTHOR]

Link layer network coding (LLNC) promises to provide high throughput in relay networks through combining packets at the relays and trading communication for computation. The emerging area of physical layer network coding (PLNC) exploits the electromagnetic nature of signals and eliminates the need for addition at the packet level, while making signal design and coding schemes adaptable to the channel conditions. Although network coding has been extensively studied recently, physical layer network coding has not received the attention it deserves. Several recent works introduced the pollution attack at the network layer; however, the network performance at the physical layer with pollution attacks has not been evaluated before. The main challenge with the pollution attack involves propagation of the corrupted packets in an epidemic manner, which degrades performance of the network. As PLNC schemes boost up the network throughput, a thorough study evaluating this superiority to the LLNC scheme in presence of an intruder is necessary. The robustness of both schemes towards an attack have been studied in this article. [ABSTRACT FROM AUTHOR]

The effect of osmotic stress on sugar transport was investigated in Clone 9 epithelial cells, which express the glucose uniporter GLUT1, and in 3T3-L1 adipocytes, which express both GLUT1 and GLUT4. An acute hyperosmotic shock increased the uptake of sugars in both cell types. In Clone 9 cells, this was followed by a regulatory volume increase (RVI) response. Stimulation of transport was rapid and reversible, with half-lives (t1/2) for stimulation of 2-deoxy-D-glucose uptake of 5.6±0.9 (n=6) and 22.7±1.5 (n=4) min for Clone 9 cells and adipocytes respectively. The effect was dose dependent, reaching a maximum at 1.1 osM of 2.9±0.1-fold (n=3) for Clone 9 cells and 8.2±0.8-fold (n=3) for adipocytes. In the latter, this stimulation correlated with translocation of the glucose transporter isoform GLUT4 to the cell surface and was not significantly different from that elicited by 160 nM insulin (7.6±1.2-fold, n=3). The effect of osmotic shock was not, however, influenced by inhibitors of either phosphoinositide 3-kinase (PI 3-kinase) (wortmannin, 250 nM) or of p38 mitogen-activated protein kinase (p38 MAP kinase) (SB203580, 20 µM), which reportedly prevent GLUT4 translocation and/or activation by insulin respectively. These inhibitors also had no effect on the stimulation of transport by osmotic shock in Clone 9 cells. However, in contrast to adipocytes, the effect of osmotic shock on glucose transport in Clone 9 cells reflected primarily a change in the intrinsic activity of cell surface transporters and there was only a minor change in their subcellular distribution as assessed by cell immunostaining or no change as assessed by surface biotinylation. These results indicate that the response of cells to osmotic shock can involve changes both in transporter activity and location. The signal transduction pathways involved include neither PI 3-kinase nor the classical, osmotically-activated component, p38 MAP kinase. [ABSTRACT FROM AUTHOR]

Human intoxication with the seafood poison ciguatoxin, a dinoflagellate polyether that activates voltage-gated sodium channels (NaV), causes ciguatera, a disease characterised by gastrointestinal and neurological disturbances. We assessed the activity of the most potent congener, Pacific ciguatoxin-1 (P-CTX-1), on NaV1.1-1.9 using imaging and electrophysiological approaches. Although P-CTX-1 is essentially a non-selective NaV toxin and shifted the voltage-dependence of activation to more hyperpolarising potentials at all NaV subtypes, an increase in the inactivation time constant was observed only at NaV1.8, while the slope factor of the conductance-voltage curves was significantly increased for NaV1.7 and peak current was significantly increased for NaV1.6. Accordingly, P-CTX-1-induced visceral and cutaneous pain behaviours were significantly decreased after pharmacological inhibition of NaV1.8 and the tetrodotoxin-sensitive isoforms NaV1.7 and NaV1.6, respectively. The contribution of these isoforms to excitability of peripheral C- and A-fibre sensory neurons, confirmed using murine skin and visceral single-fibre recordings, reflects the expression pattern of NaV isoforms in peripheral sensory neurons and their contribution to membrane depolarisation, action potential initiation and propagation. [ABSTRACT FROM AUTHOR]