Responses Of Central Neurons Research Articles

Lnc-Pim1 Promotes Neurite Outgrowth and Regeneration of Neuron-Like Cells Following ACR-Induced Neuronal Injury.

Decreased regenerative capacity of central nervous system neurons is the main cause for failure of damaged neuron regeneration and functional recovery. Long noncoding RNAs (lncRNAs) are abundant in mammalian transcriptomes, and many time- and tissue-specific lncRNAs are thought to be closely related to specific biological functions. The promoting effect of Pim-1 gene on neural differentiation and regeneration has been documented, but the effect and mechanism of its neighbor gene Lnc-Pim1 in regulating the response of central neurons to injury remain unclear. RT-PCR in this study demonstrated that the expression of Lnc-Pim1 was upregulated in acrylamide (ACR)-induced neuronal injury. FISH and nucleus-cytoplasmic assay demonstrated that Lnc-Pim1 was mainly expressed in the neuron cytoplasm, with a small amount in the nucleus. Western blot analysis proved that Lnc-Pim1 overexpression induced by the lentivirus vector could promote neurite outgrowth in Neuro-2a cells by activating the Erk1/2 signal pathway, and improve neurite regeneration of injured neurons by upregulating GAP-43 and β-Ⅲ tubulin protein expression. However, silencing Lnc-Pim1 expression by interfering RNA could effectively downregulate the GAP-43 and β-Ⅲ tubulin protein expression, and inhibit neurite growth of neurons. In addition, CHIRP-MS was performed to identify several potential targets of Lnc-Pim1 involved in the regulation of neurite regeneration of injured neurons. In conclusion, our study demonstrated that Lnc-Pim1 is a potential lnc-RNA, playing an important role in regulating central nerve regeneration.

Optic Nerve Crush Injury in Rodents to Study Retinal Ganglion Cell Neuroprotection and Regeneration.

Optic nerve crush injury is a useful model for studying the response of central nervous system neurons (CNS) to injury. A particular focus of this model has been to elucidate therapeutic factors in promoting neuroprotection and axon regeneration after injury. Here we describe a step-by-step protocol in accessing the optic nerve and creating a crush injury. This can be used to create a reproducible model to study the response of retinal ganglion cells (RGC), the main projection neurons of the eye, to injury.

Specialization of Neurons with Different Response Patterns in the Mouse Mus musculus Auditory Midbrain and Primary Auditory Cortex during Communication Call Processing

Wriggling call produced by mouse pups when struggling in the nest is one of the mouse early ontogenesis communicative vocalization. Processing of these signals by auditory midbrain and primary auditory cortex neurons with different response patterns was the subject of this study. Responses of single neurons evoked by wriggling call models and a series of models consisting of 4 stimuli with different interstimulus intervals (0–1000 ms) were recorded extracellularly. A third of central nucleus neurons in the inferior colliculus showed a spectral facilitation in responses to various two- and three-tone combinations of the wriggling call frequency components. About 80% of such combination-sensitive neurons had tonic characteristics of responses, i.e. tonic, phasic-tonic, pauser and long-latency discharges. A study of responses of central nucleus neurons to a series of wriggling call models showed that at short interstimulus intervals (0–50 ms) responses to the 2nd–4th signals in a series were completely suppressed or significantly decreased in two-thirds of the recorded neurons, i.e. there arose adaptation to a series of sounds. Such neurons had mainly phasic discharges. In a third of neurons, adaptation did not arise; these neurons were tonically discharging. All neurons in the primary auditory cortex (anterior and primary auditory fields) demonstrated adaptation in responses to a series of wriggling calls. Discharges of neurons were phasic.

Cerebellar Prediction of the Dynamic Sensory Consequences of Gravity

As we go about our everyday activities, our brain computes accurate estimates of both our motion relative to the world and our orientation relative to gravity. However, how the brain then accounts for gravity as we actively move and interact with our environment is not yet known. Here, we provide evidence that, although during passive movements, individual cerebellar output neurons encode representations of head motion and orientation relative to gravity, these gravity-driven responses are cancelled when head movement is a consequence of voluntary generated movement. In contrast, the gravity-driven responses of primary otolith and semicircular canal afferents remain intact during both active and passive self-motion, indicating the attenuated responses of central neurons are not inherited from afferent inputs. Taken together, our results are consistent with the view that the cerebellum builds a dynamic prediction (e.g., internal model) of the sensory consequences of gravity during active self-motion, which in turn enables the preferential encoding of unexpected motion to ensure postural and perceptual stability.

(131) - Determining the response of central amygdala dynorphin neurons to stress and pain

The central amygdala (CeA) is a critical structure for emotional regulation in response to stress- and pain-related behaviors. Recently, much work has focused on deciphering the role distinct CeA cell-types play in appetitive and aversive behaviors. Here, we seek to dissect the function of CeA neurons expressing the neuropeptide dynorphin (Dyn+), the endogenous ligand for the kappa opioid receptor. To genetically identify Dyn+ neurons, we use a Cre-dependent tdTomato reporter mouse. Using this approach, we report distinct patterns of c-fos expression in these neurons following an acute 30-minute restraint stress paradigm and in response to a Complete Freund's Adjuvant inflammatory pain challenge. These studies suggest that CeA Dyn+ may not acutely respond to aversive stimuli. To examine the response of these neurons to chronic pain challenges we are using in vivo fiber photometry to monitor calcium signals over extended sampling periods. To test the sufficiency of this system to drive behaviors, we used in vivo optogenetics to photostimulate dynorphinergic neurons in the central amygdala in a real-time place preference paradigm. We find that selective photostimulation of dynorphinergic neurons in the central amygdala produces a frequency-dependent real-time aversion. This latter finding suggests that CeA Dyn+ neurons may be able to promote aversive behaviors. More work will be necessary to determine whether these neurons naturally drive such behavioral responses in times of stress or pain. Understanding the properties of the dynorphin/kappa opioid system in the context of chronic stress and pain will provide valuable insight into potential intervention strategies for these neurological and neuropsychiatric disorders.

Targeting the central projection of the dural trigeminovascular system for migraine prophylaxis

Migraine abortives likely target both peripheral-dural and central trigeminovascular mechanisms in mediating their therapeutic effects. However, in preclinical assays, many migraine preventives have little success at inhibiting similar trigeminovascular-mediated peripheral changes within the dural microenvironment. In addition, their effects on central trigeminovascular neuronal responses are largely unknown. Using a validated preclinical model of acute dural-intracranial (migraine-like) head pain, using Sprague Dawley rats, we tested whether migraine preventives suppress ongoing firing of central trigeminocervical neurons, and evoked responses to cranial neurovascular activation. Flunarizine, sodium valproate, propranolol, and amitriptyline, all dose-dependently inhibited ongoing spontaneous firing of dural trigeminovascular neurons, and differentially affected neuronal responses to intracranial-dural and extracranial-cutaneous somatosensory stimulation. Lamotrigine, only effective in the treatment of migraine aura, did not affect responses. These data provide a mechanistic rationale for the clinical effects of migraine preventives in the treatment of migraine, via the modulation of dural-responsive central trigeminovascular neurons. Also, given their limited effect on peripheral dural vasdilatory responses, these data also suggest that migraine preventives specifically target central, rather than peripheral, components of trigeminal neurovascular mechanisms involved in migraine pathophysiology, to mediate their preventive action. Finally, these data further validate this preclinical model of central trigeminovascular activation to screen migraine preventives.

Sumoylation of NaV1.2 Channels Mediates the Early Response to Acute Hypoxia in Central Neurons

The mechanism for the earliest response of central neurons to hypoxia-an increase in voltage-gated sodium current (INa)-has been unknown. Here, we show that hypoxia activates the Small Ubiquitin-like Modifier (SUMO) pathway in rat cerebellar granule neurons (CGN) and that SUMOylation of NaV1.2 channels increases INa. The time-course for SUMOylation of single NaV1.2 channels at the cell surface and changes in INa coincide, and both are prevented by mutation of NaV1.2-Lys38 or application of a deSUMOylating enzyme. Within 40 s, hypoxia-induced linkage of SUMO1 to the channels is complete, shifting the voltage-dependence of channel activation so that depolarizing steps evoke larger sodium currents. Given the recognized role of INa in hypoxic brain damage, the SUMO pathway and NaV1.2 are identified as potential targets for neuroprotective interventions.

SUMOylation of NaV1.2 channels mediates the early response to acute hypoxia in central neurons.

The mechanism for the earliest response of central neurons to hypoxia-an increase in voltage-gated sodium current (INa)-has been unknown. Here, we show that hypoxia activates the Small Ubiquitin-like Modifier (SUMO) pathway in rat cerebellar granule neurons (CGN) and that SUMOylation of NaV1.2 channels increases INa. The time-course for SUMOylation of single NaV1.2 channels at the cell surface and changes in INa coincide, and both are prevented by mutation of NaV1.2-Lys38 or application of a deSUMOylating enzyme. Within 40 s, hypoxia-induced linkage of SUMO1 to the channels is complete, shifting the voltage-dependence of channel activation so that depolarizing steps evoke larger sodium currents. Given the recognized role of INa in hypoxic brain damage, the SUMO pathway and NaV1.2 are identified as potential targets for neuroprotective interventions.

Responses of non-eye-movement central vestibular neurons to sinusoidal yaw rotation in compensated macaques after unilateral semicircular canal plugging.

After vestibular labyrinth injury, behavioral measures of vestibular performance recover to variable degrees (vestibular compensation). Central neuronal responses after unilateral labyrinthectomy (UL), which eliminates both afferent resting activity and sensitivity to movement, have been well-studied. However, unilateral semicircular canal plugging (UCP), which attenuates angular-velocity detection while leaving afferent resting activity intact, has not been extensively studied. The current study reports response properties of yaw-sensitive non-eye-movement rhesus macaque vestibular neurons after compensation from UCP. The responses at a series of frequencies (0.1-2 Hz) and peak velocities (15-210°/s) were compared between neurons recorded before and at least 6 wk after UCP. The gain (sp/s/°/s) of central type I neurons (responding to ipsilateral yaw rotation) on the side of UCP was reduced relative to normal controls at 0.5 Hz, ±60°/s [0.48 ± 0.30 (SD) normal, 0.32 ± 0.15 ipsilesion; 0.44 ± 0.2 contralesion]. Type II neurons (responding to contralateral yaw rotation) after UCP have reduced gain (0.40 ± 0.27 normal, 0.35 ± 0.25 ipsilesion; 0.25 ± 0.18 contralesion). The difference between responses after UCP and after UL is primarily the distribution of type I and type II neurons in the vestibular nuclei (type I neurons comprise 66% in vestibular nuclei normally; 51% ipsilesion UCP; 59% contralesion UCP; 38% ipsilesion UL; 65% contralesion UL) and the magnitude of the responses of type II neurons ipsilateral to the lesion. These differences suggest that the need to compensate for unilateral loss of resting vestibular nerve activity after UL necessitates a different strategy for recovery of dynamic vestibular responses compared to after UCP.

Electrophysiological Identification of Central Sensitization in Patients with Chronic Prostatitis.

Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS) is a chronic pain condition and a com­mon problem in urology clinics. Although many different etiologies and mechanisms exist, the exact cause of the disease has been unknown. Central sensitization (CS) is defined as an augmentation of responsiveness of central cortical neurons to input from peripheral nociceptive structures. Somato-sensory evoked potentials (SEPs) is an electroneurophysiological method to assess cortical activity in somatosensory area of brain related to sensorial stimuli. We aimed to determine the presence of CS using the SEPs of dorsal penile nerve stimulation in patients with CP/CPPS. Seventeen male patients diagnosed CP/CPPS and 17 male healthy controls were pro­spectively included in the study. For SEP study, electrical stimulus was applied with penile ring electrodes. Re­cording electrodes were placed as active to Cz' and reference electrode on Fz' according to the 10-20 Interna­tional System. Latency of N50 was defined as the second negative (up-ward) deflection of the W-shaped averaged cortical waveform. N50 latencies were significantly shortened in the patient group compared to the healthy controls (P < .001). These results support the presence of central sensitization because of exaggerated trans-mission of pain sensation to the somatosensory cortex. Therefore, normalization of transmission might be an important step in treatment of pain in patients with CP/CPPS. This study can be counted as an important guiding on pathogenesis and treatment of disease.

Lack of Evidence for Central Sensitization in Idiopathic, Non-Traumatic Neck Pain: A Systematic Review

Background: Chronic neck pain is a common problem with a poorly understood pathophysiology. Often no underlying structural pathology can be found and radiological imaging findings are more related to age than to a patient’s symptoms. Besides its common occurrence, chronic idiopathic neck pain is also very disabling with almost 50% of all neck pain patients showing moderate disability at long-term follow-up. Central sensitization (CS) is defined as “an amplification of neural signaling within the central nervous system that elicits pain hypersensitivity,” “increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input,” or “an augmentation of responsiveness of central neurons to input from unimodal and polymodal receptors.” There is increasing evidence for involvement of CS in many chronic pain conditions. Within the area of chronic idiopathic neck pain, there is consistent evidence for the presence and clinical importance of CS in patients with traumatic neck pain, or whiplash-associated disorders. However, the majority of chronic idiopathic neck pain patients are unrelated to a traumatic injury, and hence are termed chronic idiopathic non-traumatic neck pain. When comparing whiplash with idiopathic non-traumatic neck pain, indications for different underlying mechanisms are found. Objective: The goal of this article was to review the existing scientific literature on the role of CS in patients with chronic idiopathic non-traumatic neck pain. Study Design: Systematic review. Setting: All selected studies were case control studies. Methods: A systematic search of existing, relevant literature was performed via the electronic databases Medline, Embase, Web of Science, Cinahl, PubMed, and Google Scholar. All titles and abstracts were checked to identify relevant articles. An article was considered eligible if it met following inclusion criteria: (1) participants had to be human adults (&gt; 18 years) diagnosed with idiopathic non-traumatic chronic (present for at least 3 months) neck pain; (2) papers had to report outcomes related to CS; and (3) articles had to be full-text reports or original research (no abstracts, case-reports, reviews, meta-analysis, letters, or editorials). Results: Six articles were found eligible after screening the title, abstract and – when necessary – the full text for in- and exclusion criteria. All selected studies were case-control studies. Overall, results regarding the presence of CS were divergent. While the majority of patients with chronic traumatic neck pain (i.e. whiplash) are characterized by CS, this is not the case for patients with chronic idiopathic neck pain. The available evidence suggests that CS is not a major feature of chronic idiopathic neck pain. Individual cases might have CS pain, but further work should reveal how they can be characterized. Limitations: Very few studies available. Conclusions: Literature about CS in patients with chronic idiopathic non-traumatic neck pain is rare and results from the available studies provide an inconclusive message. CS is not a characteristic feature of chronic idiopathic and non-traumatic neck pain, but can be present in some individuals of the population. In the future a subgroup with CS might be defined, but based on current knowledge it is not possible to characterize this subgroup. Such information is important in order to provide targeted treatment. Key words: Central sensitization, hypersensitivity, chronic pain, neck pain, idiopathic, nontraumatic, pressure pain thresholds, review

Influence of stimulus and oral adaptation temperature on gustatory responses in central taste-sensitive neurons.

The temperature of taste stimuli can modulate gustatory processing. Perceptual data indicate that the adapted temperature of oral epithelia also influences gustation, although little is known about the neural basis of this effect. Here, we electrophysiologically recorded orosensory responses (spikes) to 25°C (cool) and 35°C (warm) solutions of sucrose (0.1 and 0.3 M), NaCl (0.004, 0.1, and 0.3 M), and water from taste-sensitive neurons in the nucleus of the solitary tract in mice under varied thermal adaptation of oral epithelia. Conditions included presentation of taste stimuli isothermal to adaptation temperatures of 25°C (constant cooling) and 35°C (constant warming), delivery of 25°C stimuli following 35°C adaptation (relative cooling), and presentation of 35°C stimuli following 25°C adaptation (relative warming). Responses to sucrose in sucrose-oriented cells (n = 15) were enhanced under the constant and relative warming conditions compared with constant cooling, where contiguous cooling across adaptation and stimulus periods induced the lowest and longest latency responses to sucrose. Yet compared with constant warming, cooling sucrose following warm adaptation (relative cooling) only marginally reduced activity to 0.1 M sucrose and did not alter responses to 0.3 M sucrose. Thus, warmth adaptation counteracted the attenuation in sucrose activity associated with stimulus cooling. Analysis of sodium-oriented (n = 25) neurons revealed adaptation to cool water, and cooling taste solutions enhanced unit firing to 0.004 M (perithreshold) NaCl, whereas warmth adaptation and stimulus warming could facilitate activity to 0.3 M NaCl. The concentration dependence of this thermal effect may reflect a dual effect of temperature on the sodium reception mechanism that drives sodium-oriented cells.

Responses of non-eye movement central vestibular neurons to sinusoidal horizontal translation in compensated macaques after unilateral labyrinthectomy

After vestibular labyrinth injury, behavioral deficits partially recover through the process of vestibular compensation. The present study was performed to improve our understanding of the physiology of the macaque vestibular system in the compensated state (>7 wk) after unilateral labyrinthectomy (UL). Three groups of vestibular nucleus neurons were included: pre-UL control neurons, neurons ipsilateral to the lesion, and neurons contralateral to the lesion. The firing responses of neurons sensitive to linear acceleration in the horizontal plane were recorded during sinusoidal horizontal translation directed along six different orientations (30° apart) at 0.5 Hz and 0.2 g peak acceleration (196 cm/s(2)). This data defined the vector of best response for each neuron in the horizontal plane, along which sensitivity, symmetry, detection threshold, and variability of firing were determined. Additionally, the responses of the same cells to translation over a series of frequencies (0.25-5.0 Hz) either in the interaural or naso-occipital orientation were obtained to define the frequency response characteristics in each group. We found a decrease in sensitivity, increase in threshold, and alteration in orientation of best responses in the vestibular nuclei after UL. Additionally, the phase relationship of the best neural response to translational stimulation changed with UL. The symmetry of individual neuron responses in the excitatory and inhibitory directions was unchanged by UL. Bilateral central utricular neurons still demonstrated two-dimension tuning after UL, consistent with spatio-temporal convergence from a single vestibular end-organ. These neuronal data correlate with known behavioral deficits after unilateral vestibular compromise.

Blunted Peripheral and Central Responses to Gastric Mechanical and Electrical Stimulations in Diet-induced Obese Rats

Background/AimsThe increase in the prevalence of obesity is attributed to increased food intake and decreased physical activity in addition to genetic factors. Altered gut functions have been reported in obese subjects, whereas, little is known on the possible alterations in brain-gut interactions in obesity. The aim of the study was to explore possible alterations in gastric myoelectrical activity, gastric emptying, autonomic functions and central neuronal responses to gastric stimulations in diet-induced obese rats.MethodsGastric myoelectrical activity, gastric emptying and heart rate variability were recorded in lean and obese rats; extracellular neuronal activity in the ventromedial hypothalamus and its responses to gastric stimulations were also assessed.Results(1) Gastric emptying was significantly accelerated but gastric myoelectrical activity was not altered in obese rats; (2) the normal autonomic responses to feeding were absent in obese rats, suggesting an impairment of postprandial modulation of autonomic functions; and (3) central neuronal responses to gastric stimulations (both balloon distention and electrical stimulation) were blunted in obese rats, suggesting impairment in the brain-gut interaction.ConclusionsIn diet-induced obese rats, gastric emptying is accelerated, postprandial modulations of autonomic functions is altered and central neuronal responses to gastric stimulations are attenuated. These alterations in peripheral, autonomic and brain-gut interactions may help better understand pathogenesis of obesity and develop novel therapeutic approaches for obesity.

Responses of central vestibular neurons to sinusoidal yaw rotation in compensated macaques after unilateral labyrinthectomy

After vestibular labyrinth injury, behavioral measures of vestibular function partially recover through the process of vestibular compensation. The present study was performed to improve our understanding of the physiology of macaque vestibular nucleus neurons in the compensated state (>6 wk) after unilateral labyrinthectomy (UL). The responses of neurons to sinusoidal yaw rotation at a series of frequencies (0.1-2.0 Hz) and peak velocities (7.5-210°/s) were examined to determine how the behavior of these cells differed from those in animals with intact labyrinths. The sensitivity of neurons responding to ipsilateral rotation (type I) did not differ between the intact and injured sides after UL, although this sensitivity was lower bilaterally after lesion than before lesion. The sensitivity of neurons that increase firing with contralateral rotation (type II) was higher ipsilateral to the UL than before lesion or in the nucleus contralateral to the UL. UL did not increase asymmetry in the responses of individual type I or II neurons to ipsilateral vs. contralateral rotation, nor does it change the power law relationship between neuronal firing and level of stimulation. Increased sensitivities of contralesional type I neurons to the remaining vestibular nerve input and increased efficacy of inhibitory vestibular commissures projecting to the ipsilesional vestibular nucleus appear to be responsible for recovery of dynamic function of central vestibular neurons in compensated animals. The portion of type I neurons on the ipsilesional side is reduced in compensated animals, which likely accounts for the asymmetries in vestibular reflexes and perception that characterize vestibular function after UL.

Pharmacodynamic Effects of a d-Amino Acid Oxidase Inhibitor Indicate a Spinal Site of Action in Rat Models of Neuropathic Pain

Inhibition of d-amino acid oxidase (DAAO) activity is a potential target for the treatment of chronic pain. Here we characterized the effects of systemic administration of the DAAO inhibitor 4H-furo[3,2-b]pyrrole-5-carboxylic acid (SUN) in rat models of neuropathic and inflammatory pain. Oral administration of SUN dose dependently attenuated tactile allodynia induced by ligation of the L5 spinal nerve (SNL) and similarly reversed thermal hyperalgesia produced by chronic constriction injury. In addition, SUN was efficacious against complete Freund's adjuvant-induced thermal hyperalgesia. In these models, maximal reversal of pain-related behaviors corresponded with maximum rates of increase in brain and plasma d-serine concentrations, indicative of full inhibition of DAAO activity. To investigate the possible site(s) of action, we recorded spontaneous nerve activity and mechanically evoked responses of central spinal cord dorsal horn neurons and compared these with spontaneous activity of peripheral dorsal root filaments in anesthetized SNL model animals. Oral SUN reduced spontaneous activity in both central and peripheral recordings at doses and pretreatment times that corresponded to reduced mechanical allodynia in behavioral experiments. After intravenous administration of SUN, the onset of action for this central effect was rapid (maximal effects within 30 minutes), but was abolished by severing afferent inputs to the dorsal horn. Overall, these results indicate that inhibition of DAAO in peripheral afferent spinal circuits reduced spontaneous neuronal activity to attenuate pain-related behaviors in rat models of neuropathic and inflammatory pain.

Management of chronic sensitization, from drugs to physical therapy

Over the past decades, scientific understanding of unexplained chronic pain disorders has increased substantially. Several chronic musculoskeletal pain disorders may be explained by alterations in central nervous system processing. More specifically, the responsiveness of central neurons to input from unimodal and polymodal receptors is augmented, resulting in a pathophysiological state corresponding to central sensitization, characterized by generalized or widespread hypersensitivity. Central sensitization encompasses altered sensory processing in the brain, impaired functioning of top-down anti-nociceptive mechanisms, and (over)activation of top-down and bottom-up pain facilitatory pathways which augment nociceptive transmission. Importantly, a different ‘pain signature’ arises in the brain of those with chronic musculoskeletal pain and central sensitization. Given the increasing evidence supporting the clinical significance of central sensitization in those in a wide variety of disorders, including chronic whiplash associated disorders, chronic tension-type headache and migraine among others, the awareness is growing that desensitising the central nervous system should be a treatment target in these patients. Besides pharmacological options, rehabilitation (consisting of pain physiology education, stress management and exercise therapy) and neurotechnology options (e.g. Transcranial magnetic stimulation, TENS, virtual reality) offer interesting perspectives.

Modulation of gastrointestinal vagal neurocircuits by hyperglycemia

Glucose sensing within autonomic neurocircuits is critical for the effective integration and regulation of a variety of physiological homeostatic functions including the co-ordination of vagally-mediated reflexes regulating gastrointestinal (GI) functions. Glucose regulates GI functions via actions at multiple sites of action, from modulating the activity of enteric neurons, endocrine cells, and glucose transporters within the intestine, to regulating the activity and responsiveness of the peripheral terminals, cell bodies and central terminals of vagal sensory neurons, to modifying both the activity and synaptic responsiveness of central brainstem neurons. Unsurprisingly, significant impairment in GI functions occurs in pathophysiological states where glucose levels are dysregulated, such as diabetes. A substantial obstacle to the development of new therapies to modify the disease, rather than treat the symptoms, are the gaps in our understanding of the mechanisms by which glucose modulates GI functions, particularly vagally-mediated responses and a more complete understanding of disease-related plasticity within these neurocircuits may open new avenues and targets for research.

Calcium Imaging and Optical Manipulation of Neuronal Activity in Axolotl using a LED-Based Microscope

Here we introduce a novel fluorescence microscope concept which expands the application of functional fluorescence imaging and further enables optical manipulation of biological samples. Taking advantage of the LED technique allows a space saving housing of multiple light sources and illumination at various wavelengths. Furthermore, the microscope provides an optical separation into two independently controllable excitation pathways enabling a simultaneous illumination of different regions which are adjustable in size. Image detection is realized via a super resolution high speed camera that allows high resolution image capturing (2560x2160) at rates up to 100 Hz. Moreover, we implemented a voice-coil driven high NA objective to ensure z-movement at maximum speed and precision. The multiple LED arrangement and the separation of excitation pathways therefore facilitate the usage of multiple imaging approaches at the same time.To test the performance of the microscope we used in vitro whole head preparations of Ambystoma mexicanum tadpoles. This preparation allows studying neuronal systems with all sensory pathways intact and can be maintained up to one week. Thus, we were able to use calcium imaging to record sensory evoked neuronal responses of central vestibular neurons elicited by electric stimulation of specific semicircular canals. Further, to quantify the glutamate uncaging efficiency we calculated the required light intensity and duration to optically evoke action potentials by patching those neurons. Finally, we could show that by means of spatially separating calcium imaging and glutamate uncaging we were able to manipulate ipsilateral semicircular canal evoked calcium responses by optically activating contralateral inhibitory/excitatory pathways.

Roux‐en‐Y Gastric Bypass Surgery Increases The Response Of Central Vagal Neurons To Satiety Neuropeptides

Roux‐en‐Y gastric bypass surgery (GBS) is the most effective treatment for morbid obesity although the effects on brainstem neurons responsible for vagal control of the viscera are unknown. The aim of the present study was to investigate the effects of obesity and GBS on the pharmacological responses of rat dorsal motor nucleus of the vagus (DMV) neurons.4‐week old Sprague‐Dawley rats were fed a high fat diet (60% kcal from fat) for 44–59 weeks prior to GBS surgery. Sham rats received the same surgical protocol except intestinal manipulation was performed instead. Three weeks post‐surgery, whole‐cell patch clamp recordings were made from DMV neurons in brainstem slices (300μm) and the effects of perfusion with either GLP‐1 or CCK8s (both 100nM) on neuronal excitability were measured.In GBS rats, 5 of 5 neurons tested responded to GLP‐1 with an increase in action potential firing rate (219±35%) whereas only 2 of 9 Sham neurons were similarly responsive (P&lt;0.05). In contrast, while 3 of 6 GBS neurons responded to CCK8s with an increase in firing rate (190±21%) this was not significantly different from the response of Sham neurons (2 of 12 responsive neurons, 230±70%, P&gt;0.05).These results suggest that the effects of GBS to reset obesity‐related alterations in ingestive behavior also involves modulation of the responsiveness of central vagal neurons to gastrointestinal satiety neuropeptides.Supported by NIH DK080899