Effect of muscle length on the modulation of H reflex and inhibitory mechanisms of Ia afferent discharges during passive muscle lengthening.

The effectiveness of activated Ia afferents to discharge ᵯC-motoneurons is decreased during passive muscle lengthening compared with static and shortening muscle conditions. Evidence suggests that these regulations are explained by (1) greater post-activation depression induced by homosynaptic post-activation depression (HPAD) and (2) primary afferent depolarization (PAD). It remains uncertain whether muscle length impacts the muscle lengthening-related aspect of regulation of the effectiveness of activated Ia afferents to discharge ᵯC-motoneurons, HPAD, PAD and heteronymous Ia facilitation (HF). We conducted a study involving 15 healthy young individuals. We recorded conditioned or non-conditioned soleus Hoffmann (H) reflex with electromyography (EMG) to estimate the effectiveness of activated Ia afferents to discharge ᵯC-motoneurons, HPAD, PAD and HF during passive lengthening, shortening and static muscle conditions at short, intermediate and long lengths. Our results show that the decrease of effectiveness of activated Ia afferents to discharge ᵯC-motoneurons and increase of post-activation depression during passive muscle lengthening occur at all muscle lengths. For PAD and HF, we found that longer muscle length increases the magnitude of regulation related to muscle lengthening. To conclude, our findings support an inhibitory effect (resulting from increased post-activation depression) of muscle lengthening and longer muscle length on the effectiveness of activated Ia afferents to discharge α-motoneurons. The increase in post-activation depression associated with muscle lengthening can be attributed to the amplification of Ia afferents discharge.

What is the Vagal-Adrenal Axis?

Some recent publications have used the term "vagal-adrenal axis" to account for mechanisms involved in the regulation of inflammation by electroacupuncture. This concept proposes that efferent parasympathetic nerve fibers in the vagus directly innervate the adrenal glands to influence catecholamine secretion. Here, we discuss evidence for anatomical and functional links between the vagi and adrenal glands that may be relevant in the context of inflammation and its neural control by factors, including acupuncture. First, we find that evidence for any direct vagal parasympathetic efferent innervation of the adrenal glands is weak and likely artifactual. Second, we find good evidence that vagal afferent fibers directly innervate the adrenal gland, although their function is uncertain. Third, we highlight a wealth of evidence for indirect pathways, whereby vagal afferent signals act via the central nervous system to modify adrenal-dependent anti-inflammatory responses. Vagal afferents, not efferents, are thus the likely key to these phenomena.

Efficacy of endoscopic ultrasound-guided gastroenterostomy using self-expandable metallic stent for afferent loop syndrome: A single-center retrospective study.

BACKGROUND AND AIM: Endoscopic ultrasound-guided gastroenterostomy is a procedure used to connect the stomach and dilated afferent loop using a stent under endoscopic ultrasound for afferent loop syndrome. However, the actual efficacy and safety of this procedure remain unclear. Therefore, this retrospective study aimed to evaluate the efficacy and safety of endoscopic ultrasound-guided gastroenterostomy using a laser-cut-type fully covered self-expandable metallic stent and an anchoring plastic stent for afferent loop syndrome. METHODS: Technical and clinical success rates, adverse events, recurrent intestinal obstruction rates, time to recurrent intestinal obstruction, and technical and clinical success rates of re-intervention were evaluated in intended patients who underwent endoscopic ultrasound-guided gastroenterostomy for afferent loop syndrome from October 2018 to August 2022. RESULTS: In 25 intended patients with afferent loop syndrome who intended endoscopic ultrasound-guided gastroenterostomy, the technical success rate was 100% (25/25), whereas the clinical success rate was 96% (24/25). Two patients experienced grade ≥ 3 early adverse events, including one with intra-abdominal abscess and one with hypotension. Both events were attributed to intestinal fluid leakage. No late adverse events were observed. The recurrent intestinal obstruction rate was 32% (8/25), and the median time to recurrent intestinal obstruction was 6.5 months (95% confidence interval: 2.8-not available). The technical and clinical success rates of re-intervention were both 100% (8/8). CONCLUSIONS: Endoscopic ultrasound-guided gastroenterostomy using a fully covered self-expandable metallic stent and an anchoring plastic stent is effective and safe as a treatment procedure for afferent loop syndrome.

Sensorimotor Integration in Chronic Low Back Pain.

OBJECTIVE: Chronic low back pain (CLBP) impacts on spine movement. Altered sensorimotor integration can be involved. Afferents from the lumbo-pelvic area might be processed differently in CLBP and impact on descending motor control. This study aimed to determine whether afferents influence the corticomotor control of paravertebral muscles in CLBP. Fourteen individuals with CLBP (11 females) and 13 pain-free controls (8 females) were tested with transcranial magnetic stimulation (TMS) to measure the motor-evoked potential [MEP] amplitude of paravertebral muscles. Noxious and non-noxious electrical stimulation, and magnetic stimulation in the lumbo-sacral area were used as afferent stimuli and triggered 20 to 200 ms prior to TMS. EMG modulation elicited by afferent stimulation alone was measured to control net motoneuron excitability. MEP/EMG ratio was used as a measure of corticospinal excitability with control of net motoneuron excitability. MEP/EMG ratio was larger at 60, 80 and 100-ms intervals in CLBP compared to controls, and afferent stimulations alone reduced EMG amplitude greater in CLBP than controls at 100 ms. Our results suggest alteration in sensorimotor integration in CLBP highlighted by a greater facilitation of the descending corticospinal input to paravertebral muscles. Our results can help to optimise interventions by better targeting mechanisms.

High frequency heart rate variability is associated with sensitivity to affective touch.

C-tactile afferents (CTs) are a class of unmyelinated, mechanosensitive nerve fibre that respond optimally to skin temperature, slow moving touch typical of a caress. They are hypothesised to signal the rewarding value of affiliative tactile interactions. While CT firing frequency is positively correlated with subjective ratings of touch pleasantness, trait differences in sensitivity to the specific hedonic value of CT targeted touch have been reported. Inter-individual differences in vagally mediated, high frequency heart rate variability (HF-HRV) have been linked to variation in visual social cognition. Thus, the aim of the present study was to examine the relationship between resting state HF-HRV and sensitivity to socially relevant CT targeted touch. 58 healthy participants first had a 5-minute electrocardiogram. They then rated the pleasantness of 5 randomly presented velocities of robotically delivered touch. Three velocities fell within (1, 3, 10 cm/s) and two outside (0.3, 30 cm/s) the CT optimal range. Each velocity was delivered twice. On a group level, affective touch ratings were described by a negative quadratic function, with CT optimal velocities rated as more pleasant than slower and faster speeds. Simple regression analysis confirmed participants' HF-HRV was significantly predicted by the quadratic curve fit of their touch ratings, with higher HF-HRV associated with a better quadratic fit. These findings indicate that, in line with previous observations that higher HF-HRV is associated with enhanced sensitivity to visual social cues, trait differences in autonomic control could account for previously reported individual differences in CT sensitivity.

Immunohistochemical localization of proteins involved in exocytosis of glutamate from P2X3 purinoceptor-expressing subserosal afferent nerve endings in the rat gastric antrum.

We previously reported the presence of P2X3 purinoceptors (P2X3)-expressing subserosal afferent nerve endings consisting of net- and basket-like nerve endings in the rat gastric antrum. These nerve endings may morphologically be vagal mechanoreceptors activated by antral peristalsis. The present study investigated immunoreactivities for vesicular glutamate transporter (VGLUT) 1 and VGLUT2 as well as exocytosis-related proteins, i.e., core components of the SNARE complex (SNAP25, Stx1, and VAMP2) and synaptotagmin-1 (Syt1), in whole-mount preparations of the rat gastric antrum using double immunofluorescence. VGLUT1 immunoreactivity was not detected, whereas VGLUT2 immunoreactivity was observed in P2X3-immunoreactive subserosal nerve endings composed of both net- and basket-like endings. In net-like nerve endings, intense VGLUT2 immunoreactivity was localized in polygonal bulges of reticular nerve fibers and peripheral axon terminals. Furthermore, intense immunoreactivities for SNAP25, Stx1, and VAMP2 were localized in net-like nerve endings. Intense immunoreactivities for VAMP2 and Syt1 were observed in VGLUT2-immunoreactive net-like nerve endings. In basket-like nerve endings, VGLUT2 immunoreactivity was localized in pleomorphic terminal structures and small bulges surrounding the subserosal ganglion, whereas immunoreactivities for SNAP25, Stx1, and VAMP2 were weak in these nerve endings. VGLUT2-immunoreactive basket-like nerve endings were weakly immunoreactive for VAMP2 and Syt1. These results suggest that subserosal afferent nerve endings release glutamate by exocytosis mainly from net-like nerve endings to modulate their mechanoreceptor function.

Oxytocin Receptors on Calvarial Periosteal Innervation: Therapeutic Target for Post-Traumatic Headache?

OBJECTIVE: Following a mild traumatic brain injury (mTBI), the most prevalent and profoundly debilitating occurrence is the emergence of an acute and persistent post-traumatic headache (PTH), for which there are presently no approved treatments. A crucial gap in knowledge exists regarding the consequences of an mTBI, which could serve as a foundation for the development of therapeutic approaches. The activation of trigeminal sensory nerve terminals that innervate the calvarial periosteum (CP)-a densely innervated tissue layer covering the calvarial skull-has been implicated in both migraines and PTHs. We have previously shown that trigeminal oxytocin receptors (OTRs) may provide a therapeutic target for PTHs. This study examined the expression of oxytocin receptors on trigeminal nerves innervating the periosteum and whether these receptors might serve as a therapeutic target for PTHs using a direct application of oxytocin to the periosteum in a rodent model of PTH. METHODS: We used retrograde tracing and immunohistochemistry to determine if trigeminal ganglion (TG) neurons innervating the periosteum expressed OTRs and/or CGRPs. To model the impact of local inflammation that occurs following an mTBI, we applied chemical inflammatory mediators directly to the CP and assessed for changes in immediate-early gene expression as an indication of neuronal activation. We also determined whether mTBI would lead to expression changes to OTR levels. To determine whether these OTRs could be a viable therapeutic target, we assessed the impact of oxytocin injections into the CP in a mouse model of PTH-induced periorbital allodynia. RESULTS: The results of these experiments demonstrate the following: (1) the cell bodies of CP afferents reside in the TG and express both OTRs and CGRPs; (2) inflammatory chemical stimulation of the periosteum leads to rapid activation of TG neurons (phospho-ERK (p-ERK) expression), (3) mTBI-induced inflammation increased OTR expression compared to the sham group; and (4) administration of oxytocin into the periosteum on day 2 and day 40 blocked cutaneous allodynia for up to one hour post-administration for both acute and persistence phases in the PTH model-an effect that was preventable by the administration of an OTR antagonist. CONCLUSION: Taken together, our observations suggest that periosteal trigeminal afferents contribute to post-TBI craniofacial pain, and that periosteum tissue can be used as a potential local target for therapeutics such as oxytocin.

Transcholecystic Duodenal Drainage as an Alternative Decompression Method for Afferent Loop Syndrome: Two Case Reports.

Afferent loop syndrome (ALS) is a rare complication of gastrectomies and gastrointestinal reconstruction. This can predispose patients to fatal conditions, such as cholangitis, pancreatitis, and duodenal perforation with peritonitis. Therefore, emergency decompression is necessary to prevent these complications. Herein, we report two cases in which transcholecystic duodenal drainage, an alternative decompression treatment, was performed in ALS patients without bile duct dilatation. Two patients who underwent distal gastrectomy with Billroth II anastomosis sought consultation in an emergency department for epigastric pain and vomiting. On CT, ALS with acute pancreatitis was diagnosed. However, biliary access could not be achieved because of the absence of bile duct dilatation. To overcome this problem, a duodenal drainage catheter was placed to decompress the afferent loop after traversing the cystic duct via a transcholecystic approach. The patients were discharged without additional surgical treatment 2 weeks and 1 month after drainage.

Modulation of the neuronal response in human primary visual cortex by re-entrant projections during retinal input processing as manifest in the visual evoked potential.

Initial deflections in the visual evoked potential (VEP) reflect the neuronal process of extracting features from the retinal input; a process not modulated by re-entrant projections. Later deflections in the VEP reflect the neuronal process of combining features into an object, a process referred to as 'object closure' and modulated by re-entrant projections. Our earlier work indicated that the VEP reflects independent neuronal responses processing temporal - and spatial luminance contrast and that these responses arise from an interaction between forward and re-entrant input. In this earlier work, changing the temporal luminance contrast property of a stimulus altered its spatial luminance contrast property. We recorded the VEP in 12 volunteers viewing image pairs of a windmill, regular dartboard or an RMS dartboard rotated by either Π/4, Π/2, 3Π/4 or Π radians with respect to each other. The windmill and regular dartboard had identical white to black ratio, while the two dartboards identical contrast edges per unit area. Rotation varied temporal luminance contrast of a stimulus without affecting its spatial luminance contrast. N75, P100, N135 and P240 amplitude and latency were compared and a source localisation and temporal frequency analysis performed. P100 amplitude signals a neuronal response processing temporal luminance contrast that is modulated by re-entrant projections with fast axonal conduction velocities. N135 and P240 signal the neuronal response processing spatial luminance contrast and is modulated by re-entrant projections with slow axonal conduction velocities. The dorsal stream is interconnected by fast axonal conduction velocities, the ventral stream by slow axonal conduction velocities.

Internal hernia through the Treitz fossa after robotic pancreatoduodenectomy: pathogenesis and preventive measures.

Internal hernia through the Treitz fossa following robotic pancreatoduodenectomy is a rare but potentially serious complication. In our review of 328 cases of robotic pancreatoduodenectomies, two patients (0.6%) required repeat surgery due to internal herniation of the entire small bowel through the Treitz fossa. This complication can present as afferent loop syndrome, with symptoms including nausea, vomiting, and abdominal distension, possibly leading to cholangitis and pancreatitis. Timely diagnosis and intervention are paramount, as conservative management often fails. Preventive measures involve closing the peritoneal defect in the Treitz fossa at the end of robotic pancreatoduodenectomy, particularly in lean patients with thin mesentery who are at increased risk of internal hernia due to increased mobility of the small bowel. This technical note elucidates the pathogenesis of Treitz hernia following robotic pancreatoduodenectomy and underscores the importance of closing the peritoneal breach to prevent this rare yet potentially serious complication.

Transcutaneous auricular vagus nerve stimulation enhances short-latency afferent inhibition via central cholinergic system activation.

The present study examined the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on short-latency afferent inhibition (SAI), as indirect biomarker of cholinergic system activation. 24 healthy adults underwent intermittent taVNS (30 s on/30 s off, 30 min) or continuous taVNS at a frequency of 25 Hz (15 min) along with earlobe temporary stimulation (15 min or 30 min) were performed in random order. The efficiency with which the motor evoked potential from the abductor pollicis brevis muscle by transcranial magnetic stimulation was attenuated by the preceding median nerve conditioning stimulus was compared before taVNS, immediately after taVNS, and 15 min after taVNS. Continuous taVNS significantly increased SAI at 15 min post-stimulation compared to baseline. A positive correlation (Pearson coefficient = 0.563, p = 0.004) was observed between baseline SAI and changes after continuous taVNS. These results suggest that 15 min of continuous taVNS increases the activity of the cholinergic nervous system, as evidenced by the increase in SAI. In particular, the increase after taVNS was more pronounced in those with lower initial SAI. This study provides fundamental insight into the clinical potential of taVNS for cholinergic dysfunction.

Improving patient outcomes following vital sign monitoring protocol failure: A retrospective cohort study.

Background and Aims: Vital sign monitoring needs to be timely and correct to recognize deteriorating patients early and trigger the relevant clinical response. The aim of this study is to retrospectively evaluate compliance specifically toward the regional vital sign monitoring protocol the so called early warning score protocol (EWS-protocol) 72 h before a medical emergency team response (MET-response) and thereby illuminate whether poor compliance translates into a worse patient outcome. Methods: It was investigated all eligible patients that underwent MET responses during the calendar year 2019. The inclusion criteria encompassed somatic patients above 18 years of age admitted to the hospital and detailed evaluations of the medical records of the included patients were conducted. Results: Four hundred and twenty-nine MET-responses were included in the final analysis. EWS-protocol failure was observed for more than half the patients within all the time frames assessed. Thirty-day mortality was significantly higher for patients subject to EWS protocol failure in the timeframes 24-16, 16-8, 8-0 h before MET response. Adjusting for admission length, age, and gender, patients subject to EWS-protocol failure had an odds ratio (OR) of 1.9, 2.0, 2.1, 2.3 for mortality in the time frames 72-48, 24-16, 16-8, and 8-0 h before the MET-response, respectively. The adjusted OR for ICU-admission was 1.7, and 1.6 for patients subject to EWS-protocol failure in the time frames 16-8 and 8-0 h before MET-response, respectively. Conclusion: According to all the data analysis in this article, there is evidence that compliance toward the NEWS-protocol is poor. EWS-protocol failure is associated with a significant higher mortality and ICU-admission rate.

Afferent loop syndrome 7-years post Roux-en-Y gastrojejunostomy: An often-forgotten pancreatitis cause. A case report.

Afferent loop syndrome is a rare post-operative complication following upper gastrointestinal bypass surgeries, usually occurring within the first two weeks post-operation. This case report, however, outlines afferent loop syndrome almost a decade post-surgery, which was managed conservatively. A 54-year-old woman presented with a few days' history of epigastric pain, vomiting, and constipation. She had undergone a sleeve gastrectomy and was converted to a Roux-en-Y gastrojejunostomy for weight loss 9 and 7 years ago, respectively. Serum lipase was elevated at 1410 IU/L. Computed tomography showed high-grade proximal small bowel obstruction, involving the efferent and afferent loops of the Roux-en-Y gastric bypass. The patient was given intravenous rehydration, electrolyte replacement and had a nasogastric tube inserted. She was discharged on day 5 of admission without significant sequelae. Afferent limb syndrome should be considered in patients with altered upper gastrointestinal anatomy who present with pancreatitis, regardless of the time period post-operatively. Future guidelines should further more outline the factors indicated for surgical versus conservative management.

Detección de la infiltración de la cadena mamaria interna en pacientes con cáncer de mama mediante PET/RM con 18F-FDG y sus implicaciones terapéuticas / Detection of internal mammary chain infiltration in breast cancer patients by [18F]FDG PET/MRI: Therapy implications

Objetivo: Evaluar la tasa de detección y la implicación terapéutica de la infiltración de la cadena mamaria interna (ICMI) mediante tomografía por emisión de positrones (PET) y resonancia magnética (RM) con 18F-fluorodesoxiglucosa (18F-PET/RM) en la estadificación de pacientes con cáncer de mama. Método: Estudio prospectivo, 41 mujeres con cáncer de mama (estadio ≥ IIB) estadificadas mediante 18F-FDG-PET/RM. Estudio en dos fases: imágenes mamarias (decúbito prono), cuerpo completo (supino). Estadificación TNM por consenso entre especialista en Medicina Nuclear y Radiología. Estudio vaso aferente (VA) a cadena mamaria interna (CMI) por RM mamaria. Correlación ICMI con edad, VA-CMI, estadificación T, cuadrante, infiltración axilar y a distancia. Revaloración terapéutica en comité multidisciplinar. Resultados: Tasa de detección de ICMN de 34% (14/41), siendo 8/14 < 55 años. Todas las 14 pacientes con ICMI muestran VA-CMI, en seis de ellas (43,9%) sin VA-axilar. De 27/41 sin ICMI, en 13 (48,1%) solo VA-axilar, en los 14 restantes (51,9%) VA-axilar y VA-CMI. Un total de 57% (8/14) son multicéntricos y 42% (6/14) focales, en cuadrantes internos en 4/6 (66,7%). En 1/14 (7,1%) solo ICMI, en 9/14 (64,3%) axilar y CMI y en 4/14 (28,6%) lesiones a distancia. Decisión del comité: sin tratamiento adicional en 27/41 (65,8%), radioterapia torácica en 10/41 (24,4%) y terapia sistémica en 4/41 (9,7%). Conclusión: La tasa de detección de la ICMI en la estadificación del cáncer de mama mediante 18F-FDG PET/RM es de 34%. Son factores asociados la edad, los tumores multicéntricos, los de cuadrantes internos, la existencia de VA-CMI, la estadificación NM. La evidencia de ICMI permite la individualización de la terapia, indicando la radioterapia torácica en 24,4%.(AU)

Objective: To evaluate the detection rate and therapeutic implication of the infiltration of the internal mammary chain (IMCI) by [18F]FDG PET/MRI for staging of patients with breast cancer. Methods: Prospective study including 41 women with breast cancer (stage ≥IIB) staged by [18F]FDG PET/MR. Two-phase exam: breast imaging (prone), whole-body (supine). TNM stage assessed by peer consensus with Nuclear Medicine and Radiology specialists. Study of the afferent vessel (AV) to IMC by breast MRI. IMCI was correlated with age, AV-IMC, T stage, breast quadrants, axillary and distant infiltration. Therapeutic re-evaluation by a multidisciplinary committee. Results: IMCI detection rate of 34% (14/41), with 8/14 patients under 55 years of age. All 14 patients with IMCI showed AV-IMC, 6 of them (43.9%) without VA-axillary. Of 27/41 patients without IMCI, in 13 (48.1%) only AV-axillary was found, in the remaining 14 (51.9%), AV-axillary and AV-IMC was found. In 57% (8/14) tumours were multicentric and 42% (6/14) focal, in inner quadrants in 4/6 (66.7%). In 1/14 patient (7.1%) only IMCI was found, in 9/14 (64.3%) axillary and IMC, in 4/14 patients (28.6%) distant lesions were detected. Committee re-evaluation: no further treatment in 27/41 patients (65.8%), thoracic radiotherapy in 10/41 patients (24.4%), systemic therapy in 4/41 patients (9.7%). Conclusion: Our detection rate of IMCI in breast cancer staging by [18F]FDG PET/MR was 34%. Related factors were age, multicentric tumours, inner quadrants, detection of AV-IMC, NM staging.The evidence of IMCI allowed tailored therapy, with thoracic radiotherapy implementation in 24.4% of patients.(AU)

Interoceptive signals from the heart and coronary circulation in health and disease.

This review considers interoceptive signalling from the heart and coronary circulation. Vagal and cardiac sympathetic afferent sensory nerve endings are distributed throughout the atria, ventricles (mainly left), and coronary artery. A small proportion of cardiac receptors attached to thick myelinated vagal afferents are tonically active during the cardiac cycle. Dependent upon location, these mechanoreceptors detect fluctuations in atrial volume and coronary arterial perfusion. Atrial volume and coronary arterial signals contribute to beat-to-beat feedback control and physiological homeostasis. Most cardiac receptors are attached to thinly myelinated or nonmyelinated C fibres, many of which are unresponsive to the cardiac cycle. Of these, there are many chemically sensitive cardiac receptors which are activated during myocardial stress by locally released endogenous substances. In contrast, some tonically inactive receptors become activated by irregular ventricular wall mechanics or by distortion of the ischaemic myocardium. Furthermore, some are excited both by chemical mediators of ischaemia and wall abnormalities. Reflex responses arising from cardiac receptors attached to thinly myelinated or nonmyelinated are complex. Impulses that project centrally through vagal afferents elicit sympathoinhibition and hypotension, whereas impulses travelling in cardiac sympathetic afferents and spinal pathways elicit sympathoexcitation and hypertension. Two opposing cardiac reflexes may provide a mechanism for fine-tuning a composite haemodynamic response during myocardial stress. Sympathetic afferents provide the primary pathway for transmission of cardiac nociception to the central nervous system. However, activation of sympathetic afferents may increase susceptibility to life-threatening arrhythmias. Notably, the cardiac sympathetic afferent reflex predominates in pathophysiological states including hypertension and heart failure.

Extrasynaptic distribution of NMDA receptors in cochlear inner hair cell afferent signaling complex.

OBJECTIVE: The distribution and role of NMDA receptors is unclear in the afferent signaling complex of the cochlea. The present study aimed to examine the distribution of NMDA receptors in cochlear afferent signaling complex of the adult mouse, and their relationship with ribbon synapses of inner hair cells (IHCs) and GABAergic efferent terminals of the lateral olivocochlear (LOC). METHODS: Immunofluorescence staining in combination with confocal microscopy was used to investigate the distribution of glutamatergic NMDA and AMPA receptors in afferent terminals of SGNs, and their relationship with ribbon synapses of IHCs and GABAergic efferent terminals of LOC. RESULTS: Terminals with AMPA receptors along with Ribbons of IHC formed afferent synapses in the basal pole of IHCs, and those with NMDA receptors were mainly distributed longitudinally in the IHCs nuclei region. Significant difference was found in the distribution of NMDA and AMPA receptors in IHC afferent signaling complex (P<0.05). Some GABAergic terminals colocalized with NMDA receptors at the IHC nucleus region (P>0.05). CONCLUSION: There is significant difference in the distribution of NMDA and AMPA receptors in cochlear afferent signaling complex. NMDA receptors are present in the extra-synaptic region of ribbon synapses of IHCs, and they are related to GABA efferent terminals of the afferent signaling complex.

Spinal microcircuits go through multiphasic homeostatic compensations in a mouse model of motoneuron degeneration.

In neurological conditions affecting the brain, early-stage neural circuit adaption is key for long-term preservation of normal behaviour. We tested if motoneurons and respective microcircuits also adapt in the initial stages of disease progression in a mouse model of progressive motoneuron degeneration. Using a combination of in vitro and in vivo electrophysiology and super-resolution microscopy, we found that, preceding muscle denervation and motoneuron death, recurrent inhibition mediated by Renshaw cells is reduced in half due to impaired quantal size associated with decreased glycine receptor density. Additionally, higher probability of release from proprioceptive Ia terminals leads to increased monosynaptic excitation to motoneurons. Surprisingly, the initial impairment in recurrent inhibition is not a widespread feature of inhibitory spinal circuits, such as group I inhibitory afferents, and is compensated at later stages of disease progression. We reveal that in disease conditions, spinal microcircuits undergo specific multiphasic homeostatic compensations to preserve force output.

Mechanisms underlying the gut-brain communication: How enterochromaffin (EC) cells activate vagal afferent nerve endings in the small intestine.

How the gastrointestinal tract communicates with the brain, via sensory nerves, is of significant interest for our understanding of human health and disease. Enterochromaffin (EC) cells in the gut mucosa release a variety of neurochemicals, including the largest quantity of 5-hydroxytryptamine (5-HT) in the body. How 5-HT and other substances released from EC cells activate sensory nerve endings in the gut wall remains a major unresolved mystery. We used in vivo anterograde tracing from nodose ganglia to determine the spatial relationship between 5-HT synthesizing and peptide-YY (PYY)-synthesizing EC cells and their proximity to vagal afferent nerve endings that project to the mucosa of mouse small intestine. The shortest mean distances between single 5-HT- and PYY-synthesizing EC cells and the nearest vagal afferent nerve endings in the mucosa were 33.1 ± 14.4 µm (n = 56; N = 6) and 70.3 ± 32.3 µm (n = 16; N = 6). No morphological evidence was found to suggest that 5-HT- or PYY-containing EC cells form close morphological associations with vagal afferents endings, or varicose axons of passage. The large distances between EC cells and vagal afferent endings are many hundreds of times greater than those known to underlie synaptic transmission in the nervous system (typically 10-15 nm). Taken together, the findings lead to the inescapable conclusion that communication between 5-HT-containing EC cells and vagal afferent nerve endings in the mucosa of the mouse small intestinal occurs in a paracrine fashion, via diffusion. New and Noteworthy None of the findings here are consistent with a view that close physical contacts occur between 5-HT-containing EC cells and vagal afferent nerve endings in mouse small intestine. Rather, the findings suggest that gut-brain communication between EC cells and vagal afferent endings occurs via passive diffusion. The morphological data presented do not support the view that EC cells are physically close enough to vagal afferent endings to communicate via fast synaptic transmission.

Acute suppression of lower limb spasm by sacral afferent stimulation for people with spinal cord injury: A pilot study.

Lower limb spasm and spasticity may develop following spinal cord injury (SCI), causing hyper-excitability and increased tone, which can impact function and quality of life. Pharmaceutical interventions for spasticity may cause unwanted side effects such as drowsiness and weakness. Invasive and non-invasive electrical stimulation has been shown to reduce spasticity without these side effects. The aim of this study was to investigate the effect of sacral afferent stimulation (SAS), through surface electrical stimulation of the dorsal genital nerve (N = 7), and through implanted electrodes on the sacral afferent nerve roots, on lower limb spasm and spasticity (N = 2). Provoked spasms were interrupted with conditional SAS, where stimulation commenced following a provoked spasm, or unconditional stimulation, which was applied continuously. Conditionally and unconditionally applied SAS was shown to suppress acute provoked spasms in people with SCI. There was a statistically significant reduction in area under the curve of quadriceps electromyography during acute spasm with SAS compared to a control spasm. These results show that SAS may provide a safe, low-cost method of reducing acute spasm and spasticity in people living with SCI. SAS through implanted electrodes may also provide an additional function to sacral nerve stimulation devices.