A topographical and physiological exploration of C-tactile afferents and their response to menthol and histamine.

Unmyelinated tactile (C-tactile or CT) afferents are abundant in arm hairy skin and have been suggested to signal features of social affective touch. Here, we recorded from unmyelinated low-threshold mechanosensitive afferents in the peroneal and radial nerves. The most distal receptive fields were located on the proximal phalanx of the third finger for the superficial branch of the radial nerve and near the lateral malleolus for the peroneal nerve. We found that the physiological properties with regard to conduction velocity and mechanical threshold, as well as their tuning to brush velocity, were similar in CT units across the antebrachial (n = 27), radial (n = 8), and peroneal (n = 4) nerves. Moreover, we found that although CT afferents are readily found during microneurography of the arm nerves, they appear to be much more sparse in the lower leg compared with C-nociceptors. We continued to explore CT afferents with regard to their chemical sensitivity and found that they could not be activated by topical application to their receptive field of either the cooling agent menthol or the pruritogen histamine. In light of previous studies showing the combined effects that temperature and mechanical stimuli have on these neurons, these findings add to the growing body of research suggesting that CT afferents constitute a unique class of sensory afferents with highly specialized mechanisms for transducing gentle touch.NEW & NOTEWORHY Unmyelinated tactile (CT) afferents are abundant in arm hairy skin and are thought to signal features of social affective touch. We show that CTs are also present but are relatively sparse in the lower leg compared with C-nociceptors. CTs display similar physiological properties across the arm and leg nerves. Furthermore, CT afferents do not respond to the cooling agent menthol or the pruritogen histamine, and their mechanical response properties are not altered by these chemicals.

In Vivo Calcium Imaging Visualizes Incision-Induced Primary Afferent Sensitization and Its Amelioration by Capsaicin Pretreatment.

Previous studies have shown that infiltration of capsaicin into the surgical site can prevent incision-induced spontaneous pain like behaviors and heat hyperalgesia. In the present study, we aimed to monitor primary sensory neuron Ca2+ activity in the intact dorsal root ganglia (DRG) using Pirt-GCaMP3 male and female mice pretreated with capsaicin or vehicle before the plantar incision. Intraplantar injection of capsaicin (0.05%) significantly attenuated spontaneous pain, mechanical, and heat hypersensitivity after plantar incision. The Ca2+ response in in vivo DRG and in in situ spinal cord was significantly enhanced in the ipsilateral side compared with contralateral side or naive control. Primary sensory nerve fiber length was significantly decreased in the incision skin area in capsaicin-pretreated animals detected by immunohistochemistry and placental alkaline phosphatase (PLAP) staining. Thus, capsaicin pretreatment attenuates incisional pain by suppressing Ca2+ response because of degeneration of primary sensory nerve fibers in the skin.SIGNIFICANCE STATEMENT Postoperative surgery pain is a major health and economic problem worldwide with ∼235 million major surgical procedures annually. Approximately 50% of these patients report uncontrolled or poorly controlled postoperative pain. However, mechanistic studies of postoperative surgery pain in primary sensory neurons have been limited to in vitro models or small numbers of neurons. Using an innovative, distinctive, and interdisciplinary in vivo populational dorsal root ganglia (DRG) imaging (>1800 neurons/DRG) approach, we revealed increased DRG neuronal Ca2+ activity from postoperative pain mouse model. This indicates widespread DRG primary sensory neuron plasticity. Increased neuronal Ca2+ activity occurs among various sizes of neurons but mostly in small-diameter and medium-diameter nociceptors. Capsaicin pretreatment as a therapeutic option significantly attenuates Ca2+ activity and postoperative pain.

Prenatal Androgen Exposure Alters KNDy Neurons and Their Afferent Network in a Model of Polycystic Ovarian Syndrome.

Polycystic ovarian syndrome (PCOS), the most common endocrinopathy affecting women worldwide, is characterized by elevated luteinizing hormone (LH) pulse frequency due to the impaired suppression of gonadotrophin-releasing hormone (GnRH) release by steroid hormone negative feedback. Although neurons that co-express kisspeptin, neurokinin B, and dynorphin (KNDy cells) were recently defined as the GnRH/LH pulse generator, little is understood about their role in the pathogenesis of PCOS. We used a prenatal androgen-treated (PNA) mouse model of PCOS to determine whether changes in KNDy neurons or their afferent network underlie altered negative feedback. First, we identified elevated androgen receptor gene expression in KNDy cells of PNA mice, whereas progesterone receptor and dynorphin gene expression was significantly reduced, suggesting elevated androgens in PCOS disrupt progesterone negative feedback via direct actions upon KNDy cells. Second, we discovered GABAergic and glutamatergic synaptic input to KNDy neurons was reduced in PNA mice. Retrograde monosynaptic tract-tracing revealed a dramatic reduction in input originates from sexually dimorphic afferents in the preoptic area, anteroventral periventricular nucleus, anterior hypothalamic area and lateral hypothalamus. These results reveal 2 sites of neuronal alterations potentially responsible for defects in negative feedback in PCOS: changes in gene expression within KNDy neurons, and changes in synaptic inputs from steroid hormone-responsive hypothalamic regions. How each of these changes contribute to the neuroendocrine phenotype seen in in PCOS, and the role of specific sets of upstream KNDy afferents in the process, remains to be determined.

Ipsilateral somatic nerves mediate histamine-induced vasosensory reflex responses involving perivascular afferents in rat models.

Reflex cardiorespiratory alterations elicited after instillation of nociceptive agents intra-arterially (i.a) are termed as 'vasosensory reflex responses'. The present study was designed to evaluate such responses produced after i.a. instillation of histamine (1 mM; 10 mM; 100 mM) and to delineate the pathways i.e. the afferents and efferents mediating these responses. Blood pressure, electrocardiogram and respiratory excursions were recorded before and after injecting saline/histamine, in a local segment of femoral artery in urethane anesthetized rats. Paw edema and latencies of responses were also estimated. Separate groups of experiments were conducted to demonstrate the involvement of somatic nerves in mediating histamine-induced responses after ipsilateral femoral and sciatic nerve sectioning (+NX) and lignocaine pre-treatment (+Ligno). In addition, another set of experiments was performed after bilateral vagotomy (+VagX) and the responses after histamine instillation were studied. Histamine produced concentration-dependent hypotensive, bradycardiac, tachypnoeic and hyperventilatory responses of shorter latencies (2-7 s) favouring the neural mechanisms in eliciting the responses. Instillation of saline (time matched control) in a similar fashion produced no response, excluding the possibilities of ischemic/stretch effects. Paw edema was absent in both hind limbs indicating that the histamine did not reach the paws and did not spill out into the systemic circulation. +NX, +VagX, +Ligno attenuated histamine-induced cardiorespiratory responses significantly. These observations conclude that instillation of 10 mM of histamine produces optimal vasosensory reflex responses originating from the local vascular bed; afferents and efferents of which are mostly located in ipsilateral somatic and vagus nerves respectively.

Electromagnetic field and TGF-ß enhance the compensatory plasticity after sensory nerve injury in cockroach Periplaneta americana.

Recovery of function after sensory nerves injury involves compensatory plasticity, which can be observed in invertebrates. The aim of the study was the evaluation of compensatory plasticity in the cockroach (Periplaneta americana) nervous system after the sensory nerve injury and assessment of the effect of electromagnetic field exposure (EMF, 50 Hz, 7 mT) and TGF-ß on this process. The bioelectrical activities of nerves (pre-and post-synaptic parts of the sensory path) were recorded under wind stimulation of the cerci before and after right cercus ablation and in insects exposed to EMF and treated with TGF-ß. Ablation of the right cercus caused an increase of activity of the left presynaptic part of the sensory path. Exposure to EMF and TGF-ß induced an increase of activity in both parts of the sensory path. This suggests strengthening effects of EMF and TGF-ß on the insect ability to recognize stimuli after one cercus ablation. Data from locomotor tests proved electrophysiological results. The takeover of the function of one cercus by the second one proves the existence of compensatory plasticity in the cockroach escape system, which makes it a good model for studying compensatory plasticity. We recommend further research on EMF as a useful factor in neurorehabilitation.

A historical perspective of pulmonary rapidly adapting receptors.

Bronchopulmonary mechanosensors play an important role in the regulation of breathing and airway defense. Regarding the mechanosensory unit, investigators have conventionally adhered to 2 doctrines: one-sensor theory (one afferent fiber connects to a single sensor) and line-labeled theory. Accordingly, lung inflation activates 2 types of mechanosensors: slowly adapting receptors (SARs) and rapidly adapting receptors (RARs) that also respond to lung deflation to produce Hering-Breuer deflation reflex. RARs send signals to a particular brain region to stimulate breathing (labeled as excitatory line) and SARs to a different region to inhibit breathing (inhibitory line). Conventionally, RARs are believed to be mechanosensors, but are also stimulated by a variety of chemicals and mediators. They are activated during different disease conditions and evoke various respiratory responses. In the literature, RARs are the most debatable sensors in the airway. Recent physiological and morphological studies demonstrate that a mechanosensory unit consists of numerous sensors with 4 types, i.e., an afferent fiber connects to multiple homogeneous or heterogeneous sensors (multiple-sensor theory). In addition to SARs and RARs, there are deflation-activated receptors (DARs), which can adapt slowly or rapidly. Each type senses a specific force and generates a unique response. For example, RAR (or SAR) units may respond to deflation if they house DARs responsible for the Hering-Breuer deflation reflex. Multiple-sensor theory requires a conceptual shift because 4 different types of information from numerous sensors carried in an afferent pathway violates conventional theories. Data generated over last eight decades under one-sensor theory require re-interpretation. Mechanosensors and their reflex functions need re-definition. This detailed review of the RARs represents our understanding of RARs under the conventional doctrines, thus it provides a very useful background for interpretation of RAR properties and reflex function against the new proposed multiple-sensor theory.

Targeting presynaptic H3 heteroreceptor in nucleus accumbens to improve anxiety and obsessive-compulsive-like behaviors.

Anxiety commonly co-occurs with obsessive-compulsive disorder (OCD). Both of them are closely related to stress. However, the shared neurobiological substrates and therapeutic targets remain unclear. Here we report an amelioration of both anxiety and OCD via the histamine presynaptic H3 heteroreceptor on glutamatergic afferent terminals from the prelimbic prefrontal cortex (PrL) to the nucleus accumbens (NAc) core, a vital node in the limbic loop. The NAc core receives direct hypothalamic histaminergic projections, and optogenetic activation of hypothalamic NAc core histaminergic afferents selectively suppresses glutamatergic rather than GABAergic synaptic transmission in the NAc core via the H3 receptor and thus produces an anxiolytic effect and improves anxiety- and obsessive-compulsive-like behaviors induced by restraint stress. Although the H3 receptor is expressed in glutamatergic afferent terminals from the PrL, basolateral amygdala (BLA), and ventral hippocampus (vHipp), rather than the thalamus, only the PrL- and not BLA- and vHipp-NAc core glutamatergic pathways among the glutamatergic afferent inputs to the NAc core is responsible for co-occurrence of anxiety- and obsessive-compulsive-like behaviors. Furthermore, activation of the H3 receptor ameliorates anxiety and obsessive-compulsive-like behaviors induced by optogenetic excitation of the PrL-NAc glutamatergic afferents. These results demonstrate a common mechanism regulating anxiety- and obsessive-compulsive-like behaviors and provide insight into the clinical treatment strategy for OCD with comorbid anxiety by targeting the histamine H3 receptor in the NAc core.

Afferent renal innervation in anti-Thy1.1 nephritis in rats.

Afferent renal nerves exhibit a dual function controlling central sympathetic outflow via afferent electrical activity and influencing intrarenal immunological processes by releasing peptides such as calcitonin gene-related peptide (CGRP). We tested the hypothesis that increased afferent and efferent renal nerve activity occur with augmented release of CGRP in anti-Thy1.1 nephritis, in which enhanced CGRP release exacerbates inflammation. Nephritis was induced in Sprague-Dawley rats by intravenous injection of OX-7 antibody (1.75 mg/kg), and animals were investigated neurophysiologically, electrophysiologically, and pathomorphologically 6 days later. Nephritic rats exhibited proteinuria (169.3 ± 10.2 mg/24 h) with increased efferent renal nerve activity (14.7 ± 0.9 bursts/s vs. control 11.5 ± 0.9 bursts/s, n = 11, P < 0.05). However, afferent renal nerve activity (in spikes/s) decreased in nephritis (8.0 ± 1.8 Hz vs. control 27.4 ± 4.1 Hz, n = 11, P < 0.05). In patch-clamp recordings, neurons with renal afferents from nephritic rats showed a lower frequency of high activity following electrical stimulation (43.4% vs. 66.4% in controls, P < 0.05). In vitro assays showed that renal tissue from nephritic rats exhibited increased CGRP release via spontaneous (14 ± 3 pg/mL vs. 6.8 ± 2.8 pg/ml in controls, n = 7, P < 0.05) and stimulated mechanisms. In nephritic animals, marked infiltration of macrophages in the interstitium (26 ± 4 cells/mm2) and glomeruli (3.7 ± 0.6 cells/glomerular cross-section) occurred. Pretreatment with the CGRP receptor antagonist CGRP8-37 reduced proteinuria, infiltration, and proliferation. In nephritic rats, it can be speculated that afferent renal nerves lose their ability to properly control efferent sympathetic nerve activity while influencing renal inflammation through increased CGRP release.

TrkA inhibitor promotes motor functional regeneration of recurrent laryngeal nerve by suppression of sensory nerve regeneration.

Recurrent laryngeal nerve (RLN) injury, in which hoarseness and dysphagia arise as a result of impaired vocal fold movement, is a serious complication. Misdirected regeneration is an issue for functional regeneration. In this study, we demonstrated the effect of TrkA inhibitors, which blocks the NGF-TrkA pathway that acts on the sensory/automatic nerves thus preventing misdirected regeneration among motor and sensory nerves, and thereby promoting the regeneration of motor neurons to achieve functional recovery. RLN axotomy rat models were used in this study, in which cut ends of the nerve were bridged with polyglycolic acid-collagen tube with and without TrkA inhibitor (TrkAi) infiltration. Our study revealed significant improvement in motor nerve fiber regeneration and function, in assessment of vocal fold movement, myelinated nerve regeneration, compound muscle action potential, and prevention of laryngeal muscle atrophy. Retrograde labeling demonstrated fewer labeled neurons in the vagus ganglion, which confirmed reduced misdirected regeneration among motor and sensory fibers, and a change in distribution of the labeled neurons in the nucleus ambiguus. Our study demonstrated that TrkAi have a strong potential for clinical application in the treatment of RLN injury.

Selective impairment of slowly adapting type 1 mechanoreceptors in mice following vincristine treatment.

Loss of the sense of touch in fingertips and toes is one of the earliest sensory dysfunctions in patients receiving chemotherapy with anti-cancer drugs such as vincristine. However, mechanisms underlying this chemotherapy-induced sensory dysfunction is incompletely understood. Whisker hair follicles are tactile organs in non-primate mammals which are functionally equivalent to human fingertips. Here we used mouse whisker hair follicles as a model system and applied the pressure-clamped single-fiber recording technique to explore how vincristine treatment affect mechanoreceptors in whisker hair follicles. We showed that in vivo treatment of mice with vincristine impaired whisker tactile behavioral responses. The pressure-clamped single-fiber recordings made from whisker hair follicle afferent nerves showed that mechanical stimulations evoked three types of mechanical responses, rapidly adapting response (RA), slowly adapting type 1 response (SA1) and slowly adapting type 2 response (SA2). Vincristine treatment significantly reduced SA1 responses but did not significantly affect RA and SA2 responses. Our findings suggest that SA1 mechanoreceptors were selectively impaired by vincristine leading to the impairment of in vivo whisker tactile behavioral responses.

Satiety induced by bile acids is mediated via vagal afferent pathways.

The aim of this study was to elucidate the role and the pathways used by bile acid receptor TGR5 in transmitting satiety signals. We showed TGR5 colocalized with cholecystokinin type A (CCK-A) receptors in a subpopulation of rat nodose ganglia (NG) neurons. Intra-arterial injection of deoxycholic acid (DCA) dose-dependently increased firing rate in NG while a subthreshold dose of DCA and CCK-8 increased firing rates synergistically. TGR5-specific agonist oleanolic acid induced NG neuronal firing in a dose-dependent manner. However, the same units did not respond to GW4064, a nuclear receptor-specific agonist. Quantity of DCA-activated neurons in the hypothalamus was determined by c-Fos expression. Combining DCA and CCK-8 caused a 4-fold increase in c-Fos activation. In the arcuate nucleus, c-Fos-positive neurons coexpressed cocaine and amphetamine regulated transcript and proopiomelanocortin. DCA-induced c-Fos expression was eliminated following truncal vagotomy or silencing of TGR5 in the NG. Feeding studies showed intravenous injection of 1 µg/kg of DCA reduced food intake by 12% ± 3%, 24% ± 5%, and 32% ± 6% in the first 3 hours, respectively. Silencing of TGR5 or CCK-A receptor in the NG enhanced spontaneous feeding by 18% ± 2% and 13.5% ± 2.4%, respectively. When both TGR5 and CCK-A receptor were silenced, spontaneous feeding was enhanced by 37% ± 4% in the first 3 hours, suggesting that bile acid may have a physiological role in regulating satiety. Working in concert with CCK, bile acid synergistically enhanced satiety signals to reduce spontaneous feeding.

Carbidopa for Afferent Baroreflex Failure in Familial Dysautonomia: A Double-Blind Randomized Crossover Clinical Trial.

Afferent lesions of the arterial baroreflex occur in familial dysautonomia. This leads to excessive blood pressure variability with falls and frequent surges that damage the organs. These hypertensive surges are the result of excess peripheral catecholamine release and have no adequate treatment. Carbidopa is a selective DOPA-decarboxylase inhibitor that suppresses catecholamines production outside the brain. To learn whether carbidopa can inhibit catecholamine-induced hypertensive surges in patients with severe afferent baroreflex failure, we conducted a double-blind randomized crossover trial in which patients with familial dysautonomia received high dose carbidopa (600 mg/day), low-dose carbidopa (300 mg/day), or matching placebo in 3 4-week treatment periods. Among the 22 patients enrolled (13 females/8 males), the median age was 26 (range, 12-59 years). At enrollment, patients had hypertensive peaks to 164/116 (range, 144/92 to 213/150 mm Hg). Twenty-four hour urinary norepinephrine excretion, a marker of peripheral catecholamine release, was significantly suppressed on both high dose and low dose carbidopa, compared with placebo (P=0.0075). The 2 co-primary end points of the trial were met. The SD of systolic BP variability was reduced at both carbidopa doses (low dose: 17±4; high dose: 18±5 mm Hg) compared with placebo (23±7 mm Hg; P=0.0013), and there was a significant reduction in the systolic BP peaks on active treatment (P=0.0015). High- and low-dose carbidopa were similarly effective and well tolerated. This study provides class Ib evidence that carbidopa can reduce blood pressure variability in patients with congenital afferent baroreflex failure. Similar beneficial effects are observed in patients with acquired baroreflex lesions.

High fat diet induced obesity alters endocannabinoid and ghrelin mediated regulation of components of the endocannabinoid system in nodose ganglia.

BACKGROUND: Ghrelin and anandamide (AEA) can regulate the sensitivity of gastric vagal afferents to stretch, an effect mediated via the transient receptor potential vanilloid 1 (TPRV1) channel. High fat diet (HFD)-induced obesity alters the modulatory effects of ghrelin and AEA on gastric vagal afferent sensitivity. This may be a result of altered gastric levels of these hormones and subsequent changes in the expression of their receptors. Therefore, the current study aimed to determine the effects of ghrelin and AEA on vagal afferent cell body mRNA content of cannabinoid 1 receptor (CB1), ghrelin receptor (GHSR), TRPV1, and the enzyme responsible for the breakdown of AEA, fatty acid amide hydrolase (FAAH). METHODS: Mice were fed a standard laboratory diet (SLD) or HFD for 12wks. Nodose ganglia were removed and cultured for 14 h in the absence or presence of ghrelin or methAEA (mAEA; stable analogue of AEA). Relative mRNA content of CB1, GHSR, TRPV1, and FAAH were measured. RESULTS: In nodose cells from SLD-mice, mAEA increased TRPV1 and FAAH mRNA content, and decreased CB1 and GHSR mRNA content. Ghrelin decreased TRPV1, CB1, and GHSR mRNA content. In nodose cells from HFD-mice, mAEA had no effect on TRPV1 mRNA content, and increased CB1, GHSR, and FAAH mRNA content. Ghrelin decreased TRPV1 mRNA content and increased CB1 and GHSR mRNA content. CONCLUSIONS: AEA and ghrelin modulate receptors and breakdown enzymes involved in the mAEA-vagal afferent satiety signalling pathways. This was disrupted in HFD-mice, which may contribute to the altered vagal afferent signalling in obesity.

Cough Reflex Sensitivity in Asthmatic Children.

New knowledge about the neural aspects of cough has revealed a complex network of pathways that initiate cough. The effect of inflammation on cough neural processing occurs at multiple peripheral and central sites within the nervous system. Evidence exists that direct or indirect neuroimmune interaction induces a complex response, which can be altered by mediators released by the sensory or parasympathetic neurons and vice versa. The aim of this study was to clarify changes of cough reflex sensitivity - the activity of airway afferent nerve endings - in asthmatic children.25 children with asthma and 15 controls were submitted to cough reflex sensitivity measurement - capsaicin aerosol in doubling concentrations (from 0.61 to 1250 µmol/l) was inhaled by a single breath method. Concentrations of capsaicin causing two (C2) and five coughs (C5) were reported. Asthmatic children' (11 boys and 14 girls, mean age 9 ± 1 yrs) cough reflex sensitivity (geometric mean, with the 95 % CI) for C2 was 4.25 (2.25-8.03) µmol/l vs. control C2 (6 boys and 9 girls, mean age 8 ± 1 yrs) was 10.61 (5.28-21.32) µmol/l (p=0.024). Asthmatic children' C5 was 100.27 (49.30-203.93) µmol/l vs. control C5 56.53 (19.69-162.35) µmol/l (p=0.348). There was a statistically significant decrease of C2 (cough threshold) in the asthmatic patients relative to controls (p-value for the two-sample t-test of log(C2) for the one-sided alternative, p-value = 0.024). The 95 % confidence interval for the difference of the mean C2 in asthma vs. control, [1.004, 6.207]. For C5, the difference was not statistically significant (p-value = 0.348). There was a statistically significant decrease of cough reflex sensitivity (the activity of airway afferent nerve endings) - C2 value in the asthmatic children relative to controls.

Response of hypogastric afferent fibers to bladder distention or irritation in cats.

The goal of this study in anesthetized cats was to identify silent hypogastric nerve (HGN) afferent fibers that do not respond to bladder distention but become responsive after chemical irritation of the bladder. The HGN was split into multiple filaments small enough for recording action potentials from single or multiple afferent fibers. The bladder was distended by infusion of either saline or 0.5% acetic acid (AA) through a urethral catheter while recording intravesical pressure. A total of 90 HGN filaments from 17 cats responded to bladder distention with saline or AA. Three types of HGN afferents were identified. The first type was non-nociceptive mechano-sensitive that responded to bladder distention at normal physiological pressures (10-40 cmH2O). The second type was nociceptive mechano-sensitive that only responded to high-pressure (50-80 cmH2O) bladder distention with saline but responded to low-pressure bladder distention after sensitization with AA. The third type was chemo-sensitive nociceptive that was silent even during high-pressure bladder distention but after sensitization with AA did respond to low-pressure bladder distention. These results indicate that HGN afferents as well as pelvic nerve afferents may play a role in bladder nociception. The HGN afferent fibers that are silent during bladder distention at normal physiological pressures but become responsive after chemical irritation are important for understanding the possible pathophysiological mechanism underlying bladder allodynia in painful bladder syndrome.

KPR-5714, a Novel Transient Receptor Potential Melastatin 8 Antagonist, Improves Overactive Bladder via Inhibition of Bladder Afferent Hyperactivity in Rats.

Transient receptor potential (TRP) melastatin 8 (TRPM8) is a temperature-sensing ion channel mainly expressed in primary sensory neurons (Aδ-fibers and C-fibers in the dorsal root ganglion). In this report, we characterized KPR-5714 (N-[(R)-3,3-difluoro-4-hydroxy-1-(2H-1,2,3-triazol-2-yl)butan-2-yl]-3-fluoro-2-[5-(4-fluorophenyl)-1H-pyrazol-3-yl]benzamide), a novel and selective TRPM8 antagonist, to assess its therapeutic potential against frequent urination in rat models with overactive bladder (OAB). In calcium influx assays with HEK293T cells transiently expressing various TRP channels, KPR-5714 showed a potent TRPM8 antagonistic effect and high selectivity against other TRP channels. Intravenously administered KPR-5714 inhibited the hyperactivity of mechanosensitive C-fibers of bladder afferents and dose-dependently increased the intercontraction interval shortened by intravesical instillation of acetic acid in anesthetized rats. Furthermore, we examined the effects of KPR-5714 on voiding behavior in conscious rats with cerebral infarction and in those exposed to cold in metabolic cage experiments. Cerebral infarction and cold exposure induced a significant decrease in the mean voided volume and increase in voiding frequency in rats. Orally administered KPR-5714 dose-dependently increased the mean voided volume and decreased voiding frequency without affecting total voided volume in these models. This study demonstrates that KPR-5714 improves OAB in three different models by inhibiting exaggerated activity of mechanosensitive bladder C-fibers and suggests that KPR-5714 may provide a new and useful approach to the treatment of OAB. SIGNIFICANCE STATEMENT: TRPM8 is involved in bladder sensory transduction and plays a role in the abnormal activation in hypersensitive bladder disorders. KPR-5714, as a novel and selective TRPM8 antagonist, may provide a useful treatment for the disorders related to the hyperactivity of bladder afferent nerves, particularly in overactive bladder.

Activation of bradykinin-sensitive pericardial afferents increases systemic venous tone in conscious rats.

Our understanding of reflex regulation of veins lags behind that of the arterial system. While the cardiac sympathetic afferent reflex (CSAR) exerts control over sympathetic outflow, its effect on venous tone is not known. We tested the hypothesis that activation of pericardial bradykinin sensitive afferents elicits systemic venoconstriction. Male and female Sprague Dawley rats were chronically instrumented for measurement of arterial pressure and mean circulatory filling pressure, an index of venous tone, and with an indwelling pericardial catheter. Mean arterial pressure, heart rate and mean circulatory filling pressure responses were assessed in conscious rats in response to graded pericardial injections of bradykinin (1.5-20 µg/kg) before and after ganglionic blockade, and to intravenous norepinephrine (0.05-0.8 µg/kg). Bradykinin B2 receptor was assessed by Western blot. Pericardial bradykinin injections caused graded increases in mean arterial pressure, heart rate and mean circulatory filling pressure. These responses were markedly attenuated after autonomic blockade. The increments in mean circulatory filling pressure were attenuated in female rats. There were no differences in the venoconstrictor responses to norepinephrine or ventricular bradykinin receptor expression between male and females. We interpret these findings to indicate that activation of bradykinin sensitive pericardial afferents elicits a sexually dimorphic, autonomically mediated systemic venoconstrictor response. Differences in venous smooth muscle responses to norepinephrine or ventricular bradykinin receptor expression do not account for the sexual dimorphism. We conclude that systemic venoconstriction contributes to the overall hemodynamic response to activation of the cardiac sympathetic afferent reflex and that this effect is sexually dimorphic.

Combined therapy of gabapentin with pantoprazole exhibited better protective action against forestomach and pylorus ligation-induced gastric esophageal reflux disease in albino Wistar rats.

The current study was undertaken to evaluate the effect of combined therapy of gabapentin and pantoprazole against forestomach and pylorus ligation-induced gastric esophageal reflux disease (GERD) in albino Wistar rats. Rats were randomly divided into five groups, each group consisting of six rats, fasted for 24 h, underwent forestomach and pylorus ligation, received normal saline (3 ml/kg, p.o.), normal control, toxic control, pantoprazole (30 mg/kg, p.o.), gabapentin (50 mg/kg, p.o.), or their combination. After 10 h, animals were killed by cervical dislocation and evaluated for pH of gastric content, volume of gastric juice, total acidity, and esophagitis index. Esophageal tissues were further analyzed for biochemical parameters such as superoxide dismutase, glutathione, catalase, thiobarbituric acid reactive substances, and protein carbonyl, and scanning electron microscopy (SEM) and histopathology were used for morphological evaluation. The results show the combination therapy of gabapentin and pantoprazole significantly inhibited the volume of gastric juice and total acidity esophagitis index and significantly increased the pH of gastric juice. Treatment with gabapentin and pantoprazole exhibited maximum antioxidant effect in comparison with monotherapy. Marked protection and restoration of normal morphology was observed through SEM and histopathology in the combination therapy as compared to monotherapy. Finally, it was concluded that combination therapy of pantoprazole and gabapentin has beneficial effect against GERD.