Poster session abstractsP1. Clinical feasibility of liver-targeted peripheral ultrasound neuromodulation (pFUS) using interleaved B-mode imaging and pulsed ultrasound stimuli in type 2 diabeticsJeffrey Ashe1, John Graf1, Radhika Madhavan1, Kirk Wallace1, Victoria Cotero1, Samantha Abate1, Ram Krishna Pandey1, Raimund Herzog2, Porindla Sridhar Narayan1, David Shoudy1, Ying Fan1, Tzu-Jen Kao1, Chris Puleo1 1 GE Research, Niskayuna, NY, USA; 2 Yale University, New Haven, CT, USA Correspondence: Chris PuleoRecently it has been shown that mechanical shear waves produced by focused ultrasound pulses result in activation of mechanosensitive ion channels and modulate peripheral nerve activity. The activity of multiple classes of ion channels can be affected by the pulsed ultrasound stimuli, and these ion channels show cell and tissue specific expression and activation patterns. Unlike electromagnetic stimuli, ultrasound penetrates deeply through biological tissue and can be focused to millimeter-to-centimeter-sized volumes without affecting neighboring tissue. Furthermore, ultrasound pulses can be non-invasively image-targeted to specific anatomical locations with technologies used safely for decades in diagnostic imaging applications. However, while peripheral neuromodulation with ultrasound has been demonstrated in multiple in vitro and pre-clinical models, the methods have not yet been reported in humans. Herein, we demonstrate the use of a modified diagnostic imaging system for testing pulsed ultrasound neuromodulation in human subjects. Specifically, we test pulsed ultrasound stimulation of the hepatoportal plexus using stimulation parameters previously found to restore glucose homeostasis and improve insulin resistance in multiple pre-clinical models of type 2 diabetes. We demonstrate image-targeted neuromodulation by interleaving B-mode imaging pulses with focused pulsed stimuli and apply both human expert-based and post-hoc deep learning-based image object detection to quantify the on-target versus off-target stimulus dose (i.e., the duration of time and spatial average intensity of pulses that were aligned to the anatomical target). Finally, we report the first safety and feasibility outcomes in subjects with type 2 diabetes and discuss these outcomes in relation to our previous pre-clinical results.P3. Toward closed-loop bioelectronics: wireless power and data communication using magnetoelectric technologyFatima Alrashadan1, Zhanghao Yu1, Joshua Woods1, Kaiyuan Yang1, Jacob T. Robinson1,2,3 1Department of Electrical and Computer Engineering, Rice University, Houston, Texas, USA; 2Department of Bioengineering, Rice University, Houston, Texas, USA; 3Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA Correspondence: Jacob T. RobinsonImplantable bioelectronics has opened up a promising avenue to treat many drug-resistance neurological and psychiatric disorders by interfering directly with the nervous system. These devices deliver controlled electric stimulations to modulate the electrical activities of the nervous system or record the electrical, chemical, and physical properties for better diagnosis. Integrating implantable devices with wireless power, bidirectional communication, and biosensing functionalities could allow for the design of next-generation bioelectronics that features adaptive closed-loop systems and distributed networks of implants. Different wireless power transfer techniques (WPT) including radiofrequency (RF), inductive coupling, ultrasound, and light have demonstrated the ability to power medical implants, however, with performance trade-offs in terms of implant size, misalignment tolerance, bidirectional communication link, and the amount of power that can be delivered safely through biological tissues.Magnetoelectric (ME) is an emerging technology that has shown the potential to wirelessly power miniaturized implants (ME-BIT) to stimulate different nerve targets while demonstrating high efficiency at mm-size, high power delivery (> 1 mW) without safety issues, and high misalignment tolerance. These features are empowered by using ME material that has high power density, low mechanical resonance frequency, and high permeability to concentrate magnetic flux inside the material. However, to enable using the ME technology to design adaptive closed-loop systems, there is still a need to develop a bidirectional data communication link. One possible solution is to integrate the ME implant with one of the existing communication modalities, including, RF, near field coupling, ultrasound, or infrared, however, the addition of new components will increase the device footprint and constrain the power budget.Here, we propose a low-power communication system that utilizes the unique characteristic of the magnetoelectric material itself to establish a bidirectional link between the ME-BIT and an external transceiver. Specifically, we use the backscattered field generated by the ME film when excited by an external magnetic field as a carrier signal. To modulate this signal to encode digital data, we use an integrated circuit to change the electrical loading conditions across the ME film terminals. This carrier signal travels losslessly through the biological tissues and can be received using a magnetic receiver outside the body.Our system comprises an implantable ME-BIT (ME transducer + IC) and a custom portable transceiver. With design optimizations in data modulation and recovery, the proposed system archives an 8-kbps data rate at the 335-kHz carrier frequency, and a TRX-implant distance greater than 2 cm for a bit error rate less than 1E-3. Furthermore, we validated the proposed system for wireless stimulation and sensing and conducted Ex-vivo tests through a 1.5-cm porcine tissue.P4. High frequency electrical stimulation attenuates neuronal release of high mobility group box 1 (HMGB1) and ameliorates neuropathic painHuan Yang1, Timir B. Datta-Chaudhuri1,2,3, Sam J. George1, Bilal Haider1, Jason Wong1 Michael Brines1, Kevin J. Tracey1,2,3, and Sangeeta S. Chavan1,2,3 1Institute for Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, USA; 2Elmezzi Graduate School of Molecular Medicine, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY, USA; 3Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York, USA Correspondence: Sangeeta S. ChavanChronic pain presents a major unmet clinical problem. High-frequency electrical nerve stimulation (HFES) has achieved clinical success as an analgesic modality for pain management, but the underlying mechanism is unknown. We reasoned that HFES may inhibit neuroinflammatory mediator release by sensory neurons to reduce pain. HMGB1, a key mediator of injury- and infection-elicited inflammation, is involved in the pathogenesis of persistent pain. We recently reported that neuronal HMGB1 is required for mediating inflammation and hyperalgesia following nerve injury (Yang H et al., PNAS, 118:1-9, 2021). Here we assessed the effects of HFES in modulating HMGB1 release by sensory neurons. Using microelectrode arrays (MEAs) in cultured dorsal root ganglia (DRG) harvested from transgenic mice that express light-sensitive channel rhodopsin in sensory neurons, we observe that light-evoked HMGB1 release from DRGs is significantly reduced with HFES exposure (10 kHz, 2 mA, rectangular symmetric, biphasic, charge balanced) (HMGB1 levels in unstimulated group = 5.3 + 0.5 ng/ml; in light stimulated group = 25.8 + 6.0 vs. light + HFES = 8.2 + 2.1* pg/ml, N=6, *: P<0.01 vs. light stimulated group). In agreement, in vivo studies showed that HFES (20.6 kHz, 10 min/per day X 3 consecutive days) significantly reduces mechanical hyperalgesia and levels of HMGB1 in the inflamed paws in C57BL/6 mice that subjected to chronic constriction injury (CCI) of the sciatic nerve. HMGB1 levels in sham surgery group = 10.6 + 1.1 ng/mg protein, in CCI group = 29.0 + 3.9 vs. CCI + HFES = 12.8 + 1.6* ng/mg protein, N=10 mice per group, *P<0.001 vs. CCI group. Similar beneficial effects by HFES were observed in Sprague-Dawley rats subjected to sciatic nerve injury. Together, these results support the mechanistic insight that HFES may reset sensory neurons into a less pro-inflammatory state via inhibiting the release of neuroinflammatory mediators such as HMGB1 (supported in part by funding from TrueRelief, Santa Monica, CA; grants from NIH, NIGMS 1R35GM118182 to KJT and R01GM132672 to SSC).P5. Solid state batteries enable miniaturisation of active implanted medical devicesDenis Pasero 1Ilika, Unit 10a The Quadrangle, Abbey Park Industrial Estate, Romsey, UKCorrespondence: Denis PaseroPurpose: A new generation of miniaturised, implanted, active medical devices, possibly introduced via a catheter, is being developed by disruptive product designers. Conventional medical batteries are packaged within metallic cans for safety purposes; they are also typically primary (non-rechargeable) and must contain the whole energy required during the life of the device they power from first day of implantation. For these reasons, miniaturisation of conventional medical batteries is limited to a few 10’s of cm3. New active implanted sensing devices are being designed with less than 1 cm3 in volume, including implanted cardiac sensors, neuromodulation therapy devices, smart orthopaedics and orthodontics sensors. Millimeter-scale solid state batteries, which do not need significant packaging, have been developed to uniquely enable miniaturisation of next generation implantable devices.Methods: Solid state batteries were fabricated by physical vapour deposition and sputtering. Key developments to increase energy density used the following methods: Implement photolithography as a method for patterning the batteries sub-layers at the micron-level, enabling miniature features Thin down the substrate, i.e. the mechanical support for the batteries, enabling high energy density Stack and interconnect single cells on top of each other, to multiply the energy of the resulting battery for a same footprint Increase the cathode thickness in order to store more energy The rechargeable batteries have been developed on Ilika’s first volume manufacturing line, opened in Southampton, Hampshire in 2021, the first of its kind in the UK.Results: Ilika’s first solid state batteries were produced, down to 15 mm2 footprint and total thickness 1 mm. The batteries consisted of 6 stacked cells, interconnected in parallel, yielding a total capacity of 300 uAh and nominal voltage of 3.5V. The arial energy density of the stacked battery was measured to be approximately 12.5 uAh/mm2. Internal resistance of the full stack was measured to be about a sixth that of each single cell forming the stack, enabling peak power of a few mA. These batteries could be recharged in as little as 8 min with heating of the battery less than 2°C upon fast charging. These batteries are going through their final development stage and will go through full medical certification in 2023.Discussion: A novel technique for stacking and interconnecting solid state cells was shown to significantly increase the energy density and decrease the internal resistance of the battery stack. This development could enable further development in implanted medical sensors by providing an energy source of minimal size (mm-scale footprint and um-scale thickness), appropriate energy density for increasing functionalities and long life avoiding the risk and cost of removal.Use of rechargeable batteries for in-the-body applications have historically suffered from patient compliance with regards to regular charging. Whilst a new conversation with the patient is required, the benefit of miniaturising non-life-critical sensors which can be recharged in less than 10 minutes, is expected to outweigh the need for regular recharging.P7. Flexible, scalable high channel count stereo-electrode for recording in the human brainKeundong Lee,1 Angelique C. Paulk,2 Yun Goo Ro,1 Karen Tonsfeldt,1 Youngbin Tchoe,1 Andrew M. Bourhis,1 Jihwan Lee,1 Daniel R. Cleary,1 John S. Pezaris,2 Yoav Kfir,2 Sydney S. Cash,2 Shadi A. Dayeh1 1Integrated Electronics and Biointerfaces Laboratory, Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA 92093, USA; 2Department of Neurology, Harvard Medical School, Boston, MA, USA; Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA Correspondence: Shadi A. DayehOver the past decade, stereotactically placed electrodes have become the gold standard for deep brain recording and stimulation for a wide variety of neurological and psychiatric diseases. Current devices, however, are highly limited in their spatial resolution and ability to record from small populations let alone individual neurons. Here, we report on a novel, reconfigurable, monolithically integrated human-grade flexible depth electrode with a maximum of 128 channels and able to record from 10 cm of brain tissue. This thin, stylet-guided depth electrode is capable of recording local field potentials and single unit neuronal activity (action potentials) as validated across species and represents a major new advance in manufacturing and design approaches for a mainstay technology in clinical neurology.P8. NINDS and trans-NIH funding opportunities for technology development and translationEric Hudak, Megan Frankowski, Brooks Gross, Nick LanghalsDivision of Translational Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA Correspondence: Eric HudakThe mission of the NINDS Division of Translational Research (DTR) is to accelerate basic research findings toward patient use for neurological disorders and stroke by providing funding, expertise, and resources to the research community. DTR provides funding and resources through grants, cooperative agreements, and contracts to academic and industry researchers to advance early-stage neurological technologies, devices, and therapeutic approaches to industry adoption (i.e. investor funding and corporate partnerships).The Translational Neural Devices (TND) program within DTR has created a variety of programs that support the design, implementation, and management of research activities critical to translational challenges in the treatment of neurological disease. In addition, TND plays an active role in the NIH BRAIN Initiative, Blueprint MedTech Program, SPARC Program, and HEAL Initiative.NINDS TND is actively managing programs that support neural device therapeutics and training through grants, contracts, and consultants. These programs cover all stages of translational research from early device development and optimization to preclinical development and early clinical development. Funding opportunities and resources are actively supporting translational research in preclinical discovery and development of new therapeutic interventions for neurological disorders and stroke, as well as neuropsychiatric disorders and neurotraumatic injuries (BRAIN Initiative) and pain (HEAL Initiative). An overview of the NINDS Translational Neural Devices program and related Trans-NIH funding opportunities and resources will be presented.P9. Bioelectronic devices for in vivo recordings of metabolic information from the vagus nerveAmparo Guemes, Poppy Oldroyd, Alejandro Carnicer-Lombarte, Sam Hilton, George MalliarasBioelectronic Laboratory, Department of Engineering, University of Cambridge, Cambridge, UK Correspondence: Amparo GuemesIntroduction: Closed-loop bioelectronic medicine, which uses electrical recording and stimulation to interface with peripheral nerves, is becoming a promising strategy for the treatment of chronic diseases [1]. This multidisciplinary work presents the opportunities of bioelectronics for improving metabolic control in Type 1 diabetes by decoding metabolic clues from the cervical vagus nerve recordings.Methods: Interfacing with peripheral nerves and organs for reliable recording poses difficult challenges due to invasiveness and high risk of body rejection. Here, we compare the ability of two types of sub-millimetre cuff devices to record metabolic information from the vagus nerve: thin-film flexible devices were chosen given their potential for chronic implantation, and gold microwires were used as gold-standard. Both type of devices were implanted in vivo around the cervical vagus nerve of Sprague-Dawley rats anaesthetised under urethane. For the microwires, a region of 1mm was exposed towards the tip of PTFE coated gold microwires (75um diameter) and placed around the nerve for cuff recordings. Conformable bioelectronic devices were fabricated using thin-film technology based on conductive polymer PEDOT:PSS microelectrodes on parylene-C for high-resolution recording [2]. The devices include two ring microelectrodes to cover the circumference of the vagus nerve and 6 small contacts (100umx100um) to increase spatial resolution. In this work, we also present an improved strategy to extract information from neurograms under different metabolic conditions. The decoding methodology applies band-pass filtering (400Hz-4Khz), ECG removal based on continuous wavelet transformation (CWT), identification of action potentials and extraction of waveforms, dimensionality reduction, clustering of waveforms, extraction of metrics (spike rate, spike amplitude, inter-spike-interval), and correlation with metabolic events.Results: We have validated the ability to record nerve activity and decode metabolic information through implantation of both gold microwires and flexible devices on the vagus nerve of rodents after metabolic challenges. Using both types of devices, we predominantly found an increase in the overall firing rate or at least in one of the identified clusters corresponding to a decrease in glucose levels. No meaningful changes in the firing rate were observed on increasing or stable blood glucose concentrations. To verify that the detected spikes were of neural nature, a lidocaine bath at the exposed site was used at the end of the experiments that caused the successful elimination of the neural response.Conclusion: We demonstrate the design, fabrication, and acute implementation of new bioelectronic neural probes for recording signals from the surface of the vagus nerve. Gold microwires can be used as a gold-standard electrophysiological tool for acute recording from the vagus nerve of rats under anaesthesia, but bioelectronic flexible thin-film devices based on conductive polymers provide the best way for minimally invasive chronic implantation in awake animals. This study explores the development of new technology to interface with small peripheral nerves, and contributes to increase our understanding on the role the nervous systems plays in metabolism.[1] Guemes, A., Etienne-Cummings, R., and Georgiou, P. Bioelectronic Medicine 6(1). (2020).[2] D. Khodagholy, et al., Adv. Mat. 2011, vol 23, H268-H272.P10. A system for investigating bioelectronic therapies using a multicontact nerve cuff electrode and an implanted stimulator/recorderJoern Rickert1, Martin Schuettler1, Ivor Gillbe2, Ronny Pfeifer1, Timothy Denison3 1CorTec, Freiburg, Germany; 2Bioinduction Ltd., Bristol, UK; 3Institute of Biomedical Engineering, Department of Engineering Sciences, University of Oxford, Oxford, UK; MRC Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK Correspondence: Timothy DenisonIntroduction: The field of bioelectronic medicine has moved quickly in the past years from fundamental research on rodents to first clinical studies, e.g., for treatment of rheumatic arthritis or hypertension. New applications are on the horizon but the transfer from fundamental research to clinical studies requires hardware suitable for large animal or human use, which is not commonly available today. Here, we describe a platform suitable for investigating new biomedical treatment paradigms in large animals and humans.Methods and Materials: The platform combines the Picostim ultracompact stimulator/recorder implant system by Bioinduction (Bristol, UK), the DyNeuMo research application developed in partnership between Bioinduction and Oxford, and the AirRay electrode technology developed by CorTec (Freiburg, Germany).Results: The Picostim implant is powered by a rechargeable battery and features 8 channels of electrical stimulation (up to 15mA), neural recording, and a 3-axis accelerometer. The implant is very compact at just 7cc and is programmed remotely using an external wireless controller. The implant allows smart adaptive therapy employing circadian, motion and neural signal feedback, which are combined and processed in real time on the implant.The nerve interface consists of a novel self-sizing spiral nerve cuff electrode with 8 contacts. Two of the contacts are ring shaped, arranged at the ends of the cuff. The remaining 6 contacts are dot-shaped and describe a segmented ring in the middle of the cuff. The cuff is 18mm in length and has an inner diameter of 2.5mm. It is made from laser-micromachined soft silicone (PMDS) and platinum iridium contacts. The cuffs are attached to multi-lumen polyurethane-based cables/connectors.Conclusions: Combined, the platform can be used to develop new and more precise treatments using recording and fascicle selective stimulation on the vagus nerve as well as other nerves. Currently, preclinical versions of the system are undergoing tests and validations, and clinical versions are planned. Here, we present the technical details of the system and its application.P11. Non-invasive 40Hz sensory stimulation as a potential novel therapeutic intervention for neurodegenerative diseasesMihály Hajós1,2, Aylin Cimenser1, Xia Da1, Alyssa Boasso1, Chandran V. Seshagiri1, Holly Mrozak1, Evan Hempel1, J. Thomas Megerian1,3, Brent Vaughan1, Zach Malchano1 1Cognito Therapeutics, Cambridge, MA, USA; 2Yale University School of Medicine, New Haven, CT, USA; 3Thompson Autism Center, CHOC Children’s, Orange, CA, USA Correspondence: Mihály HajósRecent experimental findings have shown that synchronized 40 Hz gamma oscillation of neuronal networks, generated by optogenetic or sensory (e.g., visual and/or auditory) stimulation, effectively reduce pathological hallmarks of Alzheimer’s disease (AD) in transgenic mice expressing AD-related human pathological genes (Adaikkan & Tsai, 2020). Daily one-hour exposure to 40Hz visual and auditory stimulation showed reductions in brain AD plaques, hyperphosphorylated tau, neurodegeneration and brain atrophy. Treatment also prevented synaptic loss and dysfunction, leading to improved learning abilities in transgenic mice. These results initiated the development and validation of non-invasive, 40Hz sensory stimulation as a potential therapeutic intervention for AD and potentially other neurodegenerative diseases. In a 6-month long phase I/II randomized, controlled, US-based multi-center clinical trial (Overture trial; NCT03556280) the feasibility, safety, tolerability, adherence rates and efficacy of gamma sensory stimulation were evaluated using Cognito Therapeutics Gamma Sensory Stimulation System in patients with clinical presentation of AD spectrum. Participants with Mini-Mental State Examination (MMSE) scores of 14-26, were randomized 2:1 to receive daily, one-hour, 40Hz noninvasive audio-visual stimulation or sham stimulation.A total of 135 subjects were screened, of whom 74 were randomized and 53 completed (20 sham arm, 33 active arm). Daily use of the Gamma Sensory Stimulation System was confirmed to be safe with minimal side effects. MRI data demonstrated absence of Amyloid-Related Imaging Abnormalities (ARIA) in all subjects. High adherence to daily therapy was established based on device-recorded usage. Among clinical instruments assessing cognitive and functional abilities, Alzheimer's Disease Cooperative Study - Activities of Daily Living (ADCS-ADL) and MMSE scores demonstrated the most effective outcomes of the therapy. Changes in ADCS-ADL scores were statistically significant between the sham and treatment arms (P<0.0003), indicating a significant slowing in functional decline by the treatment. Similarly, participants in the active arm showed a significantly reduced decline in MMSE scores compared to sham arm subjects (p<0.013). Nighttime active durations (assessed by actigraphy) were significantly (p<0.03) reduced in the treatment arm and the opposite change was observed in the sham arm. Quantitative MRI analysis revealed a significantly reduced whole brain (p<0.01), and occipital lobe (p<0.03) volume loss, and a significantly attenuated reduction in occipital cortical thickness (p<0.01) in the active arm relative to the sham arm participants. A separate MRI analysis revealed a significant (p<0.004) preservation of white matter in active treatment arm participants compared to ADNI1 controls.Our results demonstrate that long-term, daily 40Hz sensory stimulation is safe and well tolerated. Based on the treatment’s excellent safety profile, together with beneficial clinical outcome results observed in the Overture trial, pivotal clinical trials have been planned to support clinical efficacy of gamma sensory stimulation in AD. In addition, based on significant reduction in white matter loss and brain atrophy, effects of gamma sensory stimulation should be explored in other neurodegenerative diseases as well.P13. Evoked synaptic excitatory potentials (ESAPs): a novel electrophysiological biomarker for spinal cord stimulationMahima Sharma1, Vividha Bhaskar1, Lillian Yang1, Nigel Gebodh1, Tianhe Zhang2, Rosana Esteller2, John Martin1, Marom Bikson1 1Department of Biomedical Engineering, The City College of New York, NY, USA; 2Boston Scientific Neuromodulation, Valencia, California, USA Correspondence: Marom BiksonIntroduction: Spinal cord stimulation (SCS) produces varied responses evoked by epidural electrical stimulation. Evoked responses occurring within 2 ms of stimulation are the electrically evoked compound action potentials (ECAP) that measure the activity of dorsal column axons but not necessarily a spinal circuit response. We identify a separate electrophysiological signal that occur 2-3 ms after SCS that directly reflects synaptic activity in the spinal grey matter.Methods: Anesthetized female Sprague Dawley rats (250-280g) were implanted with epidural spinal cord stimulation (SCS) leads, epidural motor cortex stimulation electrodes, epidural recoding lead, and intra-spinal penetrating recording electrode arrays, as well as electromyography (EMG) electrodes. We stimulated motor cortex or the epidural spinal cord with a train of 20 pulses (200- 40 μs pulse width, 1 Hz) and simultaneously recorded responses from epidural and intraspinal electrodes.Results: Low frequency (1 Hz) SCS produces characteristic ECAP (composed of P1, N1, and P2 waves lasting <2 ms) as well as an additional S-wave starting after the N2 and lasting ~6 ms. The S-wave has a distinct dose response and spinal topography compared to the ECAPs. CNQX (a highly selective competitive antagonist of AMPA) blocked the S-wave and its intraspinal analog but not ECAPS. Given its distinct synaptic origin, we term S-wave response an Evoked Synaptic Excitatory Potential (ESAP). Increasing SCS frequency to 50 Hz dampened ESAPs but not ECAPs, suggesting habituation.Conclusions: We recorded a sparsely, if ever, characterized evoked spinal synaptic response (ESAPs) in addition to dorsal column ECAPs that may shed insight into SCS underlying mechanisms.P15. Focused ultrasound stimulation at the spleen does not produce hemodynamic changes and does not elicit antidromic compound action potentials in the splenic nerveStefanos Zafeiropoulos1,2, Naveen Jayaprakash1, Stavros Zanos1,2 1 Elmezzi Graduate School of Molecular Medicine at Northwell Health, 350 Community Drive, Manhasset, NY 11030 USA; 2 Institute for Bioelectronic Medicine, Feinstein Institutes for Medical Research at Northwell Health, 350 Community Drive, Manhasset, NY 11030 USA Correspondence: Stavros ZanosBackground: Focused ultrasound stimulation (FUS) of nerve terminals at the spleen has anti-inflammatory effects (Cotero, 2019) and, for that reason, it may have therapeutic value in various diseases (Zachs2019, Ahmed 2020). However, its mechanism of action is still unclear. Splenic nerve stimulation elicits compound action potentials (CAPs) in the splenic nerve and transiently increases systemic arterial blood pressure (Donega, 2021). It is unknown if splenic FUS produces hemodynamic effects or elicits antidromic CAPs in the splenic nerve.Methods: Healthy rats (n=4) were anesthetized and FUS of the spleen was applied for 12 minutes at 0.83 MPa. Before, during and after FUS delivery, we measured right ventricular pressure, systemic blood pressure, and heart rate. At the same timepoints, we recorded neural activity from the splenic nerve; an i.v. LPS injection (10 μg) was performed as positive control to validate splenic nerve recordings, as LPS is known to activate the splenic nerve (MacNeil, 1996).Results: Right ventricular systolic pressure remained stable over the time course of the experiment (pre-FUS: 31.38 ± 1.35 mmHg, during FUS: 31.39 ± 1.17, post-FUS: 31.35 ± 1.35). Similarly, mean arterial pressure (pre-FUS 88.10 ± 1.95 mmHg, during FUS: 86.35 ± 1.66, post-FUS: 86.42 ± 2.71) and heart rate (pre-FUS: 254.89 ± 10.65, during FUS: 255.66 ± 12.43, post-FUS: 254.71 ± 12.9) did not change significantly. The rate of spontaneous CAPs recorded from the splenic nerve did not change with FUS (baseline: 0.28 ± 0.25 spikes/s, during FUS: 0.25 ± 0.22; paired
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