Effect of electroacupuncture on P2X3 receptor regulation in the peripheral and central nervous systems of rats with visceral pain caused by irritable bowel syndrome

The aim of this study is to investigate the role of the purinergic receptor P2X₃ in the peripheral and central nervous systems during acupuncture treatment for the visceral pain of irritable bowel syndrome (IBS). A total of 24 8-day-old Sprague–Dawley (SD) neonatal male rats (SPF grade) were stimulated using colorectal distention (CRD) when the rats were awake. The modeling lasted for 2 weeks with one stimulation per day. After 6 weeks, the rats were randomly divided into three groups of eight each: (1) the normal group (NG, n = 8); (2) the model group (MG, n = 8); and (3) the model + electroacupuncture group (EA, n = 8) that received electroacupuncture at a needling depth of 5 mm at the Shangjuxu (ST37, bilateral) and Tianshu (ST25, bilateral) acupoints. The parameters of the Han’s acupoint nerve stimulator (HANS) were as follows: sparse-dense wave with a frequency of 2/100 Hz, current of 2 mA, 20 min/stimulation, and one stimulation per day; the treatment was provided for seven consecutive days. At the sixth week after the treatment, the abdominal withdrawal reflex (AWR) score was determined; immunofluorescence and immunohistochemistry were used to measure the expression of the P2X₃ receptor in myenteric plexus neurons, prefrontal cortex, and anterior cingulate cortex; and, a real-time PCR assay was performed to measure the expression of P2X₃ messenger RNA (mRNA) in the dorsal root ganglion (DRG) and spinal cord. After stimulation with CRD, the expression levels of the P2X₃ receptor in the inter-colonic myenteric plexus, DRG, spinal cord, prefrontal cortex, and anterior cingulate cortex were upregulated, and the sensitivity of the rats to IBS visceral pain was increased. Electroacupuncture (EA) could downregulate the expression of the P2X₃ receptor and ease the sensitivity to visceral pain. The P2X₃ receptor plays an important role in IBS visceral pain. The different levels of P2X₃ in the peripheral enteric nervous system and central nervous system mediate the effects of the EA treatment of the visceral hyperalgesia of IBS.     

Effect of Autogenic Training on General Improvement in Patients with Irritable Bowel Syndrome: A Randomized Controlled Trial

Autogenic training (AT) is a useful and comprehensive relaxation technique. However, no studies have investigated the effects of AT on irritable bowel syndrome (IBS). In this study we tested the hypothesis that AT improves symptoms of IBS. Twenty-one patients with IBS were randomly assigned to AT (n = 11, 5 male, 6 female) or control therapy (n = 10, 5 male, 5 female). AT patients were trained intensively, while the control therapy consisted of discussions about patients’ meal habits and life styles. All patients answered a question related to adequate relief (AR) of IBS symptoms and four questionnaires: Self-induced IBS Questionnaire (SIBSQ), Self-reported Depression Scale (SDS), State-Trait Anxiety Inventory (STAI), and Medical Outcome Short Form 36 Health Survey (SF-36). The proportion of AR in the last AT session in the AT group (9/11, 81.8%) was significantly higher than that in the controls (3/10, 30.0%, Chi-square test, p = 0.048). Two subscales of the SF-36, i.e., social functioning and bodily pain, were significantly improved in the AT group (p < 0.05) as compared to the control group. Role emotional (p = 0.051) and general health (p = 0.068) showed a tendency for improvement in the AT group. AT may be useful in the treatment of IBS by enhancing self-control.     

Effects of electroacupuncture Zusanli (ST36) on food intake and expression of POMC and TRPV1 through afferents-medulla pathway in obese prone rats

Objective: The purpose of this study was to determine the effects of electroacupuncture (EA) ST36 on food intake and body weight in obese prone (OP) rats compared to obese resistant (OR) strain on a high fat diet. The influences of EA on mRNA levels of pro-opiomelanocortin (POMC), transient receptor potential vanilloid type-1 (TRPV1), and neuronal nitric oxide synthase (nNOS) were also examined in the medulla regions and ST36 skin tissue. Methods: Advanced EA ST36 was conducted in two sessions of 20 min separated by an 80 min interval for 7 days. Food intake and body weight were recorded in conscious rats every day. Real time PCR was conducted in the micropunches of the medulla regions and skin tissues at the end of the treatment. Results: Food intake and body weight were significantly reduced by advanced EA ST36 in OP rats, but slightly decreased in OR strain and sham-EA rats. Advanced EA ST36 produced a marked increase in POMC mRNA level in the nucleus tractus solitarius (NTS) and hypoglossal nucleus (HN) regions. TRPV1 and nNOS mRNAs were simultaneously increased in the NTS/gracile nucleus regions and in the ST36 skin regions by the EA treatment in OP rats. Conclusions: We conclude that advanced EA ST36 produces an up-regulation of anorexigenic factor POMC production in the NTS/HN, which inhibits food intake and reduces body weight. EA-induced expression of TRPV1-nNOS in the ST36 and the NTS/gracile nucleus is involved in the signal transduction of EA stimuli via somatosensory afferents-medulla pathways.     

The effect of a selective octopamine antagonist, epinastine, on pharyngeal pumping in Caenorhabditis elegans

This paper investigates the effect of epinastine, a selective octopamine antagonist in invertebrates, in Caenorhabditis elegans. Specifically, its ability to block the inhibitory action of octopamine on C. elegans-isolated pharynx was assayed. Isolated pharynxes were stimulated to pump by the addition of 500 nM 5-hydroxytryptamine (5-HT) (113 ± 2 per 30 s, n = 15). Octopamine inhibited the 5-HT-induced pumping in a concentration-dependent manner (threshold 1–5 μM) with a 61 ± 11% inhibition with 50 μM (n = 5). Epinastine (0.1 μM) antagonized the inhibitory response to octopamine (P < 0.001; n = 15). Tyramine also inhibited pharyngeal pumping induced by 5-HT but was less potent than octopamine. Tyramine, 50 μM to 1 mM, gave a transient inhibition e.g. of 40 ± 5% at 50 μM (n = 5). A higher (10 μM) concentration of epinastine was required to block the tryamine response compared with octopamine. It is concluded that epinastine selectively antagonizes the effect of octopamine on C. elegans pharynx. Further studies are required to test its selectivity for octopamine in other tissues and other nematodes.     

Effect of electroacupuncture on the cervicospinal P2X7 receptor/fractalkine/CX3CR1 signaling pathway in a rat neck-incision pain model

Increasing evidence supports that acupuncture intervention is an effective approach for intraoperative and postoperative pain. Neuron–microglia crosstalk, mediated by the purinergic P2X7 receptor (R)/fractalkine/CX3CR1 cascade in the spinal cord dorsal horn, plays a pivotal role in pain processing. However, its involvement in the analgesic effect of electroacupuncture (EA) remains unclear. In this study, a rat neck-incision pain model was established by making a longitudinal incision along the midline of the neck and subsequent repeated mechanical stimulation. EA stimulation was applied to bilateral LI18, LI4-PC6, or ST36-GB34. The thermal pain threshold, cervicospinal ATP concentration, expression levels of purinergic P2XR and P2YR subunits mRNAs, and fractalkine, CX3CR1 and p38 MAPK proteins, were detected separately. The neck incision induced strong thermal hyperalgesia and upregulation of spinal ATP within 48 h. No significant change was found in thermal hyperalgesia after a single session of EA intervention. However, a single session of EA dramatically enhanced the neck incision-induced upregulation of ATP and upregulated the expression of P2X7R, which was reversed by two sessions of EA. Two sessions of EA at bilateral LI18 or LI4-PC6 attenuated hyperalgesia significantly, accompanied with downregulation of P2X7R/fractalkine/ CX3CR1 signaling after three sessions of EA. EA stimulation of LI18 or LI4-PC6 alleviates thermal hyperalgesia in neck-incision pain rats, which may be associated with its effects in regulating the neck incision-induced increase of ATP and P2X7R and subsequently suppressing fractalkine/CX3CR1 signaling in the cervical spinal cord.     

Inhibition of Spinal Interlukin-33/ST2 Signaling and Downstream ERK and JNK Pathways in Electroacupuncture Analgesia in Formalin Mice

Although acupuncture is widely used to manage pain, it remains highly controversial, largely due to the lack of a clear mechanism for its benefits. Here, we investigated the role of IL-33, a novel interleukin (IL)-1 family member, and its receptor ST2 in the analgesic effects of electroacupuncture (EA) on formalin-induced inflammatory pain. The results showed that 1) EA stimulation of ipsilateral Zusanli (ST 36) and Yanglingquan (GB 34) acupoints for 30 min remarkably suppressed the two phases of formalin-induced spontaneous pain; 2) subcutaneous or intrathecal administration of recombinant IL-33 (rIL-33) significantly inhibited the analgesic effect of EA, whereas the ST2 antibody potentiated EA analgesia in formalin mice; 3) EA treatment decreased the up-regulation of IL-33 and ST2 protein following formalin injection; and 4) the suppression of the formalin-induced expression of spinal phosphorylated ERK and JNK induced by EA treatment was significantly attenuated following subcutaneous rIL-33 delivery, and was further decreased by the ST2 antibody. These data suggest that EA alleviates formalin-induced inflammatory pain, at least partially, by inhibiting of spinal IL-33/ST2 signaling and the downstream ERK and JNK pathways.     

Involvement of Spinal Serotonin Receptors in Electroacupuncture Anti-Hyperalgesia in an Inflammatory Pain Rat Model

We previously showed that electroacupuncture (EA) activates medulla-spinal serotonin-containing neurons. The present study investigated the effects of intrathecal 5,7-dihydroxytryptamine creatinine sulfate, a selective neurotoxin for serotonergic terminals, the 5-hydroxytryptamine 1A receptor (5-HT1AR) antagonist NAN-190 hydrobromide and the 5-HT2C receptor (5-HT2CR) antagonist SB-242,084 on EA anti-hyperalgesia. EA was given twice at acupoint GB30 after complete Freund’s adjuvant (CFA) injection into hind paw. CFA-induced hyperalgesia was measured by assessing hind paw withdrawal latency (PWL) to a noxious thermal stimulus 30 min post-EA. Serotonin depletion and the 5-HT1AR antagonist blocked EA anti-hyperalgesia; the 5-HT2CR antagonist did not. Immunohistochemical staining showed that spinal 5-HT1AR was expressed and that 5-HT2CR was absent in naive and CFA-injected animals 2.5 h post-CFA. These results show a correlation between EA anti-hyperalgesia and receptor expression. Collectively, the data show that EA activates supraspinal serotonin neurons to release 5-HT, which acts on spinal 5-HT1AR to inhibit hyperalgesia.     

Neuro-protective effects of carbamazepine on sleep patterns and head and body shakes in kainic acid-treated rats

The aim of this work was to analyze the effect of carbamazepine (CBZ) on sleep patterns and on “head and body shakes” and to determine the role of serotonin (5-HT) in a model of kainic-induced seizures. Thirty male Wistar rats (280–300 g) were used for polygraphic sleep recording. After a basal recording, the rats were allocated into three groups: kainic acid-treated animals (KA; 10 mg/kg; n = 10), carbamazepine-treated animals (CBZ; 30 mg/kg; n = 10) and animals injected with KA 30 min after pretreatment with CBZ (CBZ + KA; n = 10). Polygraphic recordings were performed for 10 h for 3 days, with the exception of the CBZ group, which were observed for 1 day. In order to measure the head and body shakes that occurred over that time, a behavioral assessment was performed in two additional groups of KA (n = 10) and CBZ + KA (n = 10) animals. After 10 h of behavioral assessment, the rats were sacrificed, and the levels of 5-HT and 5-hydroxy-indol-acetic acid (5-HIAA) were analyzed. We compared these findings with the results from a group of rats without pharmacological intervention (n = 10). All of the recordings were performed from 08:00 to 18:00 h. Data analysis: the electrographic parameters, head and body shake counting and monoamine concentrations were analyzed by an ANOVA test. Differences of *p ≤ 0.01 and **p ≤ 0.001 were considered statistically significant. Our results showed that CBZ exerted a protective effect on sleep pattern alterations induced by KA, which when administered alone caused a complete inhibition of sleep for the first 10 h after administration. Although there was a reduction in the amount of sleep after the administration of KA in CBZ-pretreated animals, sleep inhibition was incomplete. In addition, CBZ decreased the frequency of head and body shakes by 60% as compared to KA. The 5-HT and 5-HIAA levels in the pons were increased in the KA and KA + CBZ groups. Our conclusion is that in addition to decreasing seizure intensity, CBZ facilitates the partial recovery of sleep. These results suggest that CBZ provides neuro-protective effects on sleep and against seizures.     

Repeated electro-acupuncture attenuates chronic visceral hypersensitivity and spinal cord NMDA receptor phosphorylation in a rat irritable bowel syndrome model

Acupuncture has been used in clinical trials for the treatment of abdominal pain in patients with irritable bowel syndrome (IBS). However, scientific evidence is still lacking and the underlying mechanism remains largely unexplored. The aim of this study was to examine the effects of repeated administration of electro-acupuncture (EA) on chronic visceral hypersensitivity and on the phosphorylation of spinal cord N-methyl-d-aspartic acid (NMDA) receptors in a rat model of IBS. The results showed that repeated administration of EA at bilateral points of Zu-san-li (ST-36) and Shang-ju-xu (ST-37) significantly attenuated chronic visceral hypersensitivity induced in young adult rats by neonatal colon irritation. Such an effect was not seen in either of the two controls: sham-EA at ST-36 and ST-37 without electrical stimulation and EA at control points (BL-62 and tail). Furthermore, rats with chronic visceral hypersensitivity exhibited high-level expression of phosphorylated NMDA receptor subunit 1 (pNR1) in the spinal cord (L4-L5 segments), which was markedly attenuated by EA treatment. In addition, EA at ST-36 and ST-37 neither altered the pain threshold of normal rats nor affected the expression of pNR1 in the lumbosacral spinal cord. Altogether, these data indicate that the EA-mediated attenuation of chronic visceral hypersensitivity is correlated with the down-regulation of NMDA receptors phosphorylation at the spinal level.     

Schisandra chinensis reverses visceral hypersensitivity in a neonatal-maternal separated rat model

Visceral hypersensitivity is an important characteristic feature of functional gastrointestinal disorders, such as irritable bowel syndrome (IBS). This study evaluated the effect of Schisandra chinensis on visceral hyperalgesia induced by neonatal maternal separation (NMS) in an IBS rat model. The visceromotor responses to colorectal balloon distension (CRD) were measured by abdominal withdrawal reflex (AWR) and electromyographic (EMG) activities. NMS control rats (receiving vehicle) underwent aggravated visceral pain in response to CRD as compared to normal rats, evidenced by the reduced pain threshold, enhanced AWR scores and EMG responses. Treatment with a 70% ethanol extract of S. chinensis (0.3g/kg and 1.5g/kg/day) for 7 days resulted in an increase in the pain threshold (NMS control: 19.1±1.0mmHg vs low-dose: 24.8±1.3mmHg and high-dose: 25.2±1.8mmHg, p<0.01), and abolished the elevated AWR and EMG responses to CRD in NMS rats (AUC values of EMG response curve were: 1952±202 in NMS control group vs 1074±90 in low-dose group and 1145±92 in high-dose group, p<0.001), indicating that S. chinensis could reverse the visceral hypersensitivity induced by early-life stress event. The result of ELSA measurement shows that the elevated serotonin (5-HT) level in the distal colon of NMS rats returned to normal level after treatment with S. chinensis. Moreover, the increase in pain threshold in rats treated with S. chinensis was associated with a decline of the mRNA level of 5-HT(3) receptor in the distal colon. All available results demonstrate that S. chinensis can reverse visceral hypersensitivity induced by neonatal-maternal separation, and the effect may be mediated through colonic 5-HT pathway in the rat.     

Electroacupuncture alleviates diabetic neuropathic pain in rats by suppressing P2X3 receptor expression in dorsal root ganglia

Diabetic neuropathic pain (DNP) is a troublesome diabetes complication all over the world. P2X3 receptor (P2X3R), a purinergic receptor from dorsal root ganglion (DRG), has important roles in neuropathic pain pathology and nociceptive sensations. Here, we investigated the involvement of DRG P2X3R and the effect of 2 Hz electroacupuncture (EA) on DNP. We monitored the rats’ body weight, fasting blood glucose level, paw withdrawal thresholds, and paw withdrawal latency, and evaluated P2X3R expression in DRG. We found that P2X3R expression is upregulated on DNP, while 2 Hz EA is analgesic against DNP and suppresses P2X3R expression in DRG. To evaluate P2X3R involvement in pain modulation, we then treated the animals with A317491, a P2X3R specific antagonist, or α β-me ATP, a P2X3R agonist. We found that A317491 alleviates hyperalgesia, while α β-me ATP blocks EA’s analgesic effects. Our findings indicated that 2 Hz EA alleviates DNP, possibly by suppressing P2X3R upregulation in DRG.

     

L-364,718 Potentiates Electroacupuncture Analgesia Through Cck-A Receptor of Pain-Related Neurons in the Nucleus Parafascicularis

Electroacupuncture (EA) has been successfully used to alleviate pain produced by various noxious stimulus. Cholecystokinin-8 (CCK-8) is a neuropeptide involved in the mediation of pain. We have previously shown that CCK-8 could antagonize the analgesic effects of EA on pain-excited neurons (PENs) and pain-inhibited neurons (PINs) in the nucleus parafascicularis (nPf). However, its mechanism of action is not clear. In the present study, we applied behavioral and neuroelectrophysiological methods to determine whether the mechanisms of CCK-8 antagonism to EA analgesia are mediated through the CCK-A receptors of PENs and PINs in the nPf of rats. We found that focusing radiant heat on the tail of rats caused a simultaneous increase in the evoked discharge of PENs or a decrease in the evoked discharge of PINs in the nPf and the tail-flick reflex. This showed that radiant heat could induce pain. EA stimulation at the bilateral ST 36 acupoints in rats for 15 min resulted in an inhibition of the electrical activity of PEN, potentiation of the electrical activity of PIN, and prolongation in tail-flick latency (TFL), i.e. EA stimulation produced an analgesic effect. The analgesic effect of EA was antagonized when CCK-8 was injected into the intracerebral ventricle of rats. The antagonistic effect of CCK-8 on EA analgesia was reversed by an injection of CCK-A receptor antagonist L-364,718 (100 ng/μl) into the nPf of rats. Our results suggest that the pain-related neurons in the nPf have an important role in mediating EA analgesia. L-364,718 potentiates EA analgesia through the CCK-A receptor of PENs and PINs in the nPf.     

Effects of neonatal maternal separation on neurochemical and sensory response to colonic distension in a rat model of irritable bowel syndrome

Early life stress has been implicated as a risk factor for irritable bowel syndrome (IBS). We studied the effect of neonatal maternal separation on the visceromotor response and the expression of c-fos, 5-HT, and its receptors/transporters along the brain-gut axis in an animal model of IBS. Male neonatal Sprague-Dawley rats were randomly assigned to a 3-h daily maternal separation (MS) or nonhandling (NH) on postnatal days 2-21. Colorectal balloon distention (CRD) was performed for assessment of abdominal withdrawal reflex as a surrogate marker of visceral pain. Tissues from dorsal raphe nucleus in midbrain, lumbar-sacral cord, and distal colon were harvested for semiquantitative analysis of c-fos and 5-HT. The expression of 5-HT expression, 5-HT3 receptors, and 5-HT transporter were analyzed by RT-PCR. Pain threshold was significantly lower in MS than NH rats. The abdominal withdrawal reflex score in response to CRD in MS rats was significantly higher with distension pressures of 40, 60, and 80 mmHg. In MS rats, the number of c-fos-like immunoreactive nuclei at dorsal horn of lumbar-sacral spinal cord increased significantly after CRD. 5-HT content in the spinal cord of MS rats was significant higher. In the colon, both 5-HT-positive cell number and 5-HT content were comparable between MS and NH groups before CRD. Post-CRD only MS rats had significant increase in 5-HT content. Protein and mRNA expression levels of 5-HT3 receptors and 5-HT transporter were similar in MS and NH rats. Neonatal maternal separation stress predisposes rats to exaggerated neurochemical responses and visceral hyperalgesia in colon mimicking IBS.     

Human-associated fluoroquinolone-resistant Escherichia coli clonal lineages,including ST354, isolated from canine feces and extraintestinal infections in Australia

Phylogenetic group D extraintestinal pathogenic Escherichia coli (ExPEC), including O15:K52:H1 and clonal group A, have spread globally and become fluoroquinolone-resistant. Here we investigated the role of canine feces as a reservoir of these (and other) human-associated ExPEC and their potential as canine pathogens. We characterized and compared fluoroquinolone-resistant E. coli isolates originally identified as phylogenetic group D from either the feces of hospitalized dogs (n = 67; 14 dogs) or extraintestinal infections (n = 53; 33 dogs). Isolates underwent phylogenetic grouping, random amplified polymorphic DNA (RAPD) analysis, virulence genotyping, resistance genotyping, human-associated ExPEC O-typing, and multi-locus sequence typing. Five of seven human-associated sequence types (STs) exhibited ExPEC-associated O-types, and appeared in separate RAPD clusters. The largest subgroup (16 fecal, 26 clinical isolates) were ST354 (phylogroup F) isolates. ST420 (phylogroup B2); O1-ST38, O15:K52:H1-ST393, and O15:K1-ST130 (phylogroup D); and O7-ST457, and O1-ST648 (phylogroup F) were also identified. Three ST-specific RAPD sub-clusters (ST354, ST393, and ST457) contained closely related isolates from both fecal or clinical sources. Genes encoding CTX-M and AmpC β-lactamases were identified in isolates from five STs. Major human-associated fluoroquinolone-resistant ± extended-spectrum cephalosporin-resistant ExPEC of public health importance may be carried in dog feces and cause extraintestinal infections in some dogs.     

ST2 blockade mitigates peritoneal fibrosis induced by TGF‐β and high glucose

Peritoneal fibrosis (PF) is an intractable complication of peritoneal dialysis (PD) that leads to peritoneal membrane failure. This study investigated the role of suppression of tumorigenicity (ST)2 in PF using patient samples along with mouse and cell‐based models. Baseline dialysate soluble (s)ST2 level in patients measured 1 month after PD initiation was 2063.4 ± 2457.8 pg/mL; patients who switched to haemodialysis had elevated sST2 levels in peritoneal effluent (1576.2 ± 199.9 pg/mL, P = .03), which was associated with PD failure (P = .04). Baseline sST2 showed good performance in predicting PD failure (area under the receiver operating characteristic curve = 0.780, P = .001). In mice with chlorhexidine gluconate‐induced PF, ST2 was expressed in fibroblasts and mesothelial cells within submesothelial zones. In primary cultured human peritoneal mesothelial cells (HPMCs), transforming growth factor‐β treatment increased ST2, fibronectin, β‐galactosidase and Snail protein levels and decreased E‐cadherin level. Anti‐ST2 antibody administration reversed the up‐regulation of ST2 and fibronectin expression; it also reduced fibrosis induced by high glucose (100 mmol/L) in HPMCs. Thus, high ST2 level in dialysate is a marker for fibrosis and inflammation during peritoneal injury, and blocking ST2 may be an effective therapeutic strategy for renal preservation.     

Effects of Cannabinoids on Caffeine Contractures in Slow and Fast Skeletal Muscle Fibers of the Frog

The effect of cannabinoids on caffeine contractures was investigated in slow and fast skeletal muscle fibers using isometric tension recording. In slow muscle fibers, WIN 55,212-2 (10 and 5 μM) caused a decrease in tension. These doses reduced maximum tension to 67.43 ± 8.07% (P = 0.02, n = 5) and 79.4 ± 14.11% (P = 0.007, n = 5) compared to control, respectively. Tension-time integral was reduced to 58.37 ± 7.17% and 75.10 ± 3.60% (P = 0.002, n = 5), respectively. Using the CB₁ cannabinoid receptor agonist ACPA (1 μM) reduced the maximum tension of caffeine contractures by 68.70 ± 11.63% (P = 0.01, n = 5); tension-time integral was reduced by 66.82 ± 6.89% (P = 0.02, n = 5) compared to controls. When the CB₁ receptor antagonist AM281 was coapplied with ACPA, it reversed the effect of ACPA on caffeine-evoked tension. In slow and fast muscle fibers incubated with the pertussis toxin, ACPA had no effect on tension evoked by caffeine. In fast muscle fibers, ACPA (1 μM) also decreased tension; the maximum tension was reduced by 56.48 ± 3.4% (P = 0.001, n = 4), and tension-time integral was reduced by 57.81 ± 2.6% (P = 0.006, n = 4). This ACPA effect was not statistically significant with respect to the reduction in tension in slow muscle fibers. Moreover, we detected the presence of mRNA for the cannabinoid CB₁ receptor on fast and slow skeletal muscle fibers, which was significantly higher in fast compared to slow muscle fiber expression. In conclusion, our results suggest that in the slow and fast muscle fibers of the frog cannabinoids diminish caffeine-evoked tension through a receptor-mediated mechanism.     

Physiological and Genomic Consequences of Intermittent Hypoxia: Selected Contribution: Phrenic long-term facilitation requires 5-HT receptor activation during but not following episodic hypoxia

Episodic hypoxia evokes a sustained augmentation of respiratorymotor output known as long-term facilitation (LTF). Phrenic LTF isprevented by pretreatment with the 5-hydroxytryptamine (5-HT) receptorantagonist ketanserin. We tested the hypothesis that 5-HT receptoractivation is necessary for the induction but not maintenance ofphrenic LTF. Peak integrated phrenic nerve activity (Phr) wasmonitored for 1 h after three 5-min episodes of isocapnic hypoxia(arterial PO₂ = 40 ± 2 Torr; 5-minhyperoxic intervals) in four groups of anesthetized, vagotomized,paralyzed, and ventilated Sprague-Dawley rats [1) control(n = 11), 2) ketanserin pretreatment (2 mg/kg iv; n = 7), and ketanserin treatment 0 and 45 minafter episodic hypoxia (n = 7 each)]. Ketanserintransiently decreased Phr, but it returned to baseline levels within10 min. One hour after episodic hypoxia, Phr was significantlyelevated from baseline in control and in the 0- and 45-min posthypoxia ketanserin groups. Conversely, ketanserin pretreatment abolished phrenic LTF. We conclude that 5-HT receptor activation is necessary toinitiate (during hypoxia) but not maintain (following hypoxia) phrenic LTF.

     

Electroacupuncture modulates the intestinal microecology to improve intestinal motility in spinal cord injury rats

Spinal cord injury (SCI) is a disease involving gastrointestinal disorders. The underlying mechanisms of the potential protective effects of electroacupuncture (EA) and 5-hydroxytryptamine (5-HT) system on SCI remain unknown. We investigated whether EA improves gut microbial dysbiosis in SCI and regulates the 5-HT system. 16S rDNA gene sequencing was applied to investigate alterations in the gut microbiome of the rats. Faecal metabolites and the expression of the 5-HT system were detected. EA and faecal microbiota transplantation (FMT) treatment facilitated intestinal transmission functional recovery and restored the colon morphology of SCI rats. The composition of the intestinal microbiota, including numbers of phylum Proteobacteria, class Clostridia, order Bacteroidales, and genus Dorea, were amplified in SCI rats, and EA and FMT significantly reshaped the intestinal microbiota. SCI resulted in disturbed metabolic conditions in rats, and the EA and FMT group showed increased amounts of catechin compared with SCI rats. SCI inhibited 5-HT system expression in the colon, which was significantly reversed by EA and FMT treatment. Therefore, EA may ameliorate SCI by modulating microbiota and metabolites and regulate the 5-HT system. Our study provides new insights into the pathogenesis and therapy of SCI from the perspective of microbiota and 5-HT regulation.