Key pointsr Mouse chromaffin cells (MCCs) of the adrenal medulla possess fast-inactivating Nav channels whose availability alters spontaneous action potential firing patterns and the Ca 2+ -dependent secretion of catecholamines.r Here, we report MCCs expressing large densities of neuronal fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no subthreshold pacemaker currents and can be slowly inactivated by 50% upon slight membrane depolarization.r Reducing Nav1.3/Nav1.7 availability by tetrodotoxin or by sustained depolarization near rest leads to a switch from tonic to burst-firing patterns that give rise to elevated Ca 2+ -influx and increased catecholamine release.r Spontaneous burst firing is also evident in a small percentage of control MCCs. r Our results establish that burst firing comprises an intrinsic firing mode of MCCs that boosts their output. This occurs particularly when Nav channel availability is reduced by sustained splanchnic nerve stimulation or prolonged cell depolarizations induced by acidosis, hyperkalaemia and increased muscarine levels.Abstract Action potential (AP) firing in mouse chromaffin cells (MCCs) is mainly sustained by Cav1.3 L-type channels that drive BK and SK currents and regulate the pacemaking cycle. As secretory units, CCs optimally recruit Ca 2+ channels when stimulated, a process potentially dependent on the modulation of the AP waveform. Our previous work has shown that a critical determinant of AP shape is voltage-gated sodium channel (Nav) channel availability. Here, we studied the contribution of Nav channels to firing patterns and AP shapes at rest (−50 mV) and upon stimulation (−40 mV). Using quantitative RT-PCR and immunoblotting, we show that MCCs mainly express tetrodotoxin (TTX)-sensitive, fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no Na + current during slow ramp depolarizations. Time constants and the percentage of recovery from fast inactivation and slow entry into closed-state inactivation are similar to that of brain Nav1.3 and Nav1.7 channels. The fraction of available Nav channels is reduced by half after 10 mV depolarization from −50 to −40 mV. This leads to low amplitude spikes and a reduction in repolarizing K + currents inverting the net current from outward to inward during the after-hyperpolarization. When Nav channel availability is reduced by up to 20% of total, either by TTX block or steady depolarization, a switch from tonic to burst firing is observed. The spontaneous occurrence of high frequency bursts is rare under control conditions (14% of cells) but leads to major Ca 2+ -entry and increased catecholamine release. Thus, Nav1.3/Nav1.7 channel availability sets the AP shape, burst-firing initiation and regulates

Key points The vagus nerve is the largest cranial nerve and innervates many structures in the neck, thorax and abdomen. Although single‐unit recordings from the vagus nerve have been performed in experimental animals for several decades, no recordings have ever been made from the human vagus nerve. The vagus nerve is routinely stimulated clinically, yet we know little of its physiology in humans. We describe the methodology and provide preliminary results of the first intraneural single‐unit recordings from the cervical vagus in awake humans, using tungsten microelectrodes inserted into the nerve through ultrasound guidance. Abstract Intraneural microelectrodes have been used extensively to record from single somatosensory axons supplying muscle, tendons, joints and skin, as well as to record from postganglionic sympathetic axons supplying muscle and skin, in accessible peripheral nerves in awake humans. However, the vagus nerve has never been targeted, probably because of its close proximity to the carotid artery and jugular vein in the neck. Here, we report the first unitary recordings from the human cervical vagus nerve, obtained using ultrasound‐guided insertion of tungsten microelectrodes into fascicles of the nerve. We identified tonically‐active neurones in which firing rates were inversely related to heart rate (and directly related to the cardiac interval), which we classified as putative preganglionic parasympathetic axons directed to the sinoatrial node of the heart. We also recorded from tonically‐active presumed sensory axons from the airways and presumed motor axons to the larynx. This new methodology opens exciting new opportunities for studying the physiology of the human vagus nerve in health and disease.

Objective. Bioelectronic medicine is opening new perspectives for the treatment of some major chronic diseases through the physical modulation of autonomic nervous system activity. Being the main peripheral route for electrical signals between central nervous system and visceral organs, the vagus nerve (VN) is one of the most promising targets. Closed-loop VN stimulation (VNS) would be crucial to increase effectiveness of this approach. Therefore, the extrapolation of useful physiological information from VN electrical activity would represent an invaluable source for single-target applications. Here, we present an advanced decoding algorithm novel to VN studies and properly detecting different functional changes from VN signals. Approach. VN signals were recorded using intraneural electrodes in anaesthetized pigs during cardiovascular and respiratory challenges mimicking increases in arterial blood pressure, tidal volume and respiratory rate. We developed a decoding algorithm that combines discrete wavelet transformation, principal component analysis, and ensemble learning made of classification trees. Main results. The new decoding algorithm robustly achieved high accuracy levels in identifying different functional changes and discriminating among them. Interestingly our findings suggest that electrodes positioning plays an important role on decoding performances. We also introduced a new index for the characterization of recording and decoding performance of neural interfaces. Finally, by combining an anatomically validated hybrid neural model and discrimination analysis, we provided new evidence suggesting a functional topographical organization of VN fascicles. Significance. This study represents an important step towards the comprehension of VN signaling, paving the way for the development of effective closed-loop VNS systems.

Bioelectronic medicine (BM) is an emerging new approach for developing novel neuromodulation therapies for pathologies that have been previously treated with pharmacological approaches. In this review, we will focus on the neuromodulation of autonomic nervous system (ANS) activity with implantable devices, a field of BM that has already demonstrated the ability to treat a variety of conditions, from inflammation to metabolic and cognitive disorders. Recent discoveries about immune responses to ANS stimulation are the laying foundation for a new field holding great potential for medical advancement and therapies and involving an increasing number of research groups around the world, with funding from international public agencies and private investors. Here, we summarize the current achievements and future perspectives for clinical applications of neural decoding and stimulation of the ANS. First, we present the main clinical results achieved so far by different BM approaches and discuss the challenges encountered in fully exploiting the potential of neuromodulatory strategies. Then, we present current preclinical studies aimed at overcoming the present limitations by looking for optimal anatomical targets, developing novel neural interface technology, and conceiving more efficient signal processing strategies. Finally, we explore the prospects for translating these advancements into clinical practice.

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The autonomic nervous system exerts a fine beat-to-beat regulation of cardiovascular functions and is consequently involved in the onset and progression of many cardiovascular diseases (CVDs). Selective neuromodulation of the brain-heart axis with advanced neurotechnologies is an emerging approach to corroborate CVDs treatment when classical pharmacological agents show limited effectiveness. The vagus nerve is a major component of the cardiac neuroaxis, and vagus nerve stimulation (VNS) is a promising application to restore autonomic function under various pathological conditions. VNS has led to encouraging results in animal models of CVDs, but its translation to clinical practice has not been equally successful, calling for more investigation to optimize this technique. Herein we reviewed the state of the art of VNS for CVDs and discuss avenues for therapeutic optimization. Firstly, we provided a succinct description of cardiac vagal innervation anatomy and physiology and principles of VNS. Then, we examined the main clinical applications of VNS in CVDs and the related open challenges. Finally, we presented preclinical studies that aim at overcoming VNS limitations through optimization of anatomical targets, development of novel neural interface technologies, and design of efficient VNS closed-loop protocols.

The neuronal scaffold protein p140Cap was investigated during hippocampal network formation. p140Cap is present in presynaptic GABAergic terminals and its genetic depletion results in a marked alteration of inhibitory synaptic activity. p140Cap-/- cultured neurons display higher frequency of miniature inhibitory postsynaptic currents (mIPSCs) with no changes of their mean amplitude. Consistent with a potential presynaptic alteration of basal GABA release, p140Cap-/- neurons exhibit a larger synaptic vesicle readily releasable pool, without any variation of single GABAA receptor unitary currents and number of postsynaptic channels. Furthermore, p140Cap-/- neurons show a premature and enhanced network synchronization and appear more susceptible to 4-aminopyridine-induced seizures in vitro and to kainate-induced seizures in vivo. The hippocampus of p140Cap-/- mice showed a significant increase in the number of both inhibitory synapses and of parvalbumin- and somatostatin-expressing interneurons. Specific deletion of p140Cap in forebrain interneurons resulted in increased susceptibility to in vitro epileptic events and increased inhibitory synaptogenesis, comparable to those observed in p140Cap-/- mice. Altogether, our data demonstrate that p140Cap finely tunes inhibitory synaptogenesis and GABAergic neurotransmission, thus regulating the establishment and maintenance of the proper hippocampal excitatory/inhibitory balance.

21Bioelectronic medicine is opening new perspectives for the treatment of some major chronic 22 diseases through the physical modulation of autonomic nervous system activity. Being the 23 main peripheral route for electrical signals between central nervous system and visceral 24 organs, the vagus nerve (VN) is one of the most promising targets. Closed-loop 25 neuromodulation would be crucial to increase effectiveness and reduce side effects, but it 26 depends on the possibility of extracting useful physiological information from VN electrical 27 activity, which is currently very limited. 28 Here, we present a new decoding algorithm properly detecting different functional changes 29 from VN signals. They were recorded using intraneural electrodes in anaesthetized pigs 30 during cardiovascular and respiratory challenges mimicking increases in arterial blood 31 pressure, tidal volume and respiratory rate. A novel decoding algorithm was developed 32 combining discrete wavelet transformation, principal component analysis, and ensemble 33 learning made of classification trees. It robustly achieved high accuracy levels in identifying 34 different functional changes and discriminating among them. We also introduced a new 35 index for the characterization of recording and decoding performance of neural interfaces. 36Finally, by combining an anatomically validated hybrid neural model and discrimination 37 analysis, we provided new evidence suggesting a functional topographical organization of 38 VN fascicles. This study represents an important step towards the comprehension of VN 39 signaling, paving the way to the development of effective closed-loop bioelectronic systems. 40 41 Algorithm, Hybrid Modeling Framework. 44 45 46 48 of body homeostasis. In ANS peripheral nerves, afferent and efferent fibres run together, 49 providing bidirectional communication between specific circuits of the central nervous 50 system and visceral organs. The artificial modulation of this complex circuitry is the 51 challenging goal of bioelectronic medicine (BM), a highly promising alternative to some 52 limited pharmacological tretments 1-3 . Among the main ANS nerves, the vagus nerve (VN) 53 represents a privileged target as it modulates vital functions like respiration, circulation and 54 the digestion 4 . VN stimulation (VNS) of cervical segments has shown a great potential for 55 the treatment of a wide range of pathological conditions such as epilepsy 5 , chronic heart 56 failure 6 , and inflammatory diseases 7,8 . However, the formidable amount of afferent and 57 efferent signals that simultaneously cross this VN segment, the numerous VNS side-effects 9 58 and the discovery of VN involvement in the regulation of complex functions like immunity 10 59 or central neuroplasticity 11,12 highlight the need for high precision and selectivity. In an ideal 60 scenario, the therapeutic stimulation or inhibition of VN or any other ANS nerve should be: 61 a) selectively directed to specific efferent or afferent fibres and b) regulated by a ...