Neurotransmitters and Neuropeptides decrease PD-1 in T cells of healthy subjects and patients with hepatocellular carcinoma (HCC), and increase their proliferation and eradication of HCC cells

T cells of aged people, and of patients with either cancer or severe infections (including COVID-19), are often exhausted, senescent and dysfunctional, leading to increased susceptibilities, complications and mortality.Neurotransmitters and Neuropeptides bind their receptors in T cells, and induce multiple beneficial T cell functions. Yet, T cells of different people vary in the expression levels of Neurotransmitter and Neuropeptide receptors, and in the magnitude of the corresponding effects.Therefore, we performed an individual-based study on T cells of 3 healthy subjects, and 3 Hepatocellular Carcinoma (HCC) patients. HCC usually develops due to chronic inflammation. The inflamed liver induces reduction and inhibition of CD4⁺ T cells and Natural Killer (NK) cells. Immune-based therapies for HCC are urgently needed.We tested if selected Neurotransmitters and Neuropeptides decrease the key checkpoint protein PD-1 in human T cells, and increase proliferation and killing of HCC cells.First, we confirmed human T cells express all dopamine receptors (DRs), and glutamate receptors (GluRs): AMPA-GluR3, NMDA-R and mGluR. Second, we discovered that either Dopamine, Glutamate, GnRH-II, Neuropeptide Y and/or CGRP (10nM), as well as DR and GluR agonists, induced the following effects: 1. Decreased significantly both %PD-1⁺ T cells and PD-1 expression level per cell (up to 60% decrease, within 1 h only); 2. Increased significantly the number of T cells that proliferated in the presence of HCC cells (up to 7 fold increase), 3. Increased significantly T cell killing of HCC cells (up to 2 fold increase). 4. Few non-conventional combinations of Neurotransmitters and Neuropeptides had surprising synergistic beneficial effects.We conclude that Dopamine, Glutamate, GnRH-II, Neuropeptide Y and CGRP, alone or in combinations, can decrease % PD-1⁺ T cells and PD-1 expression per cell, in T cells of both healthy subjects and HCC patients, and increase their proliferation in response to HCC cells and killing of HCC cells. Yet, testing T cells of many more cancer patients is absolutely needed.Based on these findings and previous ones, we designed a novel “Personalized Adoptive Neuro-Immunotherapy”, calling for validation of safety and efficacy in clinical trials.     

Brain-mediated responses to vaginocervical stimulation in spinal cord-transected rats: role of the vagus nerves

The present study was designed to ascertain whether the vagus nerves convey functional sensory activity from the reproductive tract in rats. Previously, vaginocervical mechanostimulation (VS) was shown to increase pupil diameter (PD) and the threshold of vocalization to tail shock (Voc-T). These responses were attenuated but not abolished by combined bilateral transection of the ‘genito-spinal’ nerves (i.e. pelvic, hypogastric and pudendal). Subsequent bilateral vagotomy further reduced or abolished the residual responses. In the present study, spinal cord transection above the known level of entry of the genito-spinal nerves was combined with bilateral vagotomy. In ovariectomized rats, after spinal cord transection at thoracic 7 (T7X), lumbar 5 (L5X) levels, or sham surgery (Sh), responses to VS were measured, the vagus nerves were then transected bilaterally, and responses to VS were again measured. VS significantly increased Voc-T and PD after sham procedure or spinal cord transection at either level. Subsequent bilateral vagotomy abolished the VS-induced increase in PD in the T7X group. Due to low survival rate, the effect of vagotomy on Voc-T could not be determined. Consequently, we performed a second experiment. In non-ovariectomized rats, VS significantly increased PD but reduced Voc-T in the T7X group compared to the Sh group, and subsequent bilateral vagotomy abolished both responses. These findings provide evidence that, in the rat, the vagus nerves provide a functional sensory pathway from the reproductive tract directly to the medulla oblongata of the brain, bypassing the spinal cord.     

Neuronal-like features of TE671 cells: Presence of a functional nicotinic cholinergic receptor

The human medulloblastoma cell line TE671 has been investigated and found to have several ‘neuron-like’ properties, including the presence of a functional nicotinic receptor. The cell line TE671 is composed of at least 5 stable morphologic cell types. Resting potentials recorded with intracellular microelectrodes were low (−17 mV to −31 mV) but all cell types were capable of generating Na⁺-dependent action potentials following anode-brake stimulation. Rare spontaneous hyperpolarizing potentials, suggestive of synaptic activity, were also observed.TE671 cells were completely unresponsive to iontophoresed GABA but did respond to acetylcholine (ACh). The most common response to ACh was a depolarization accompanied by an increase in membrane conductance. When large amounts of ACh were delivered, depolarization followed by hyperpolarization was frequently observed. Depolarizing responses to ACh are abolished in Na⁺-free solution while hyperpolarizing responses to ACh were still present following the removal of both Na⁺ and Cl⁻ from the bathing solution.The depolarization response to ACh is mediated through a nicotinic cholinergic receptor. Depolarization was completely blocked in the presence of 10⁻⁶ M α-bungarotoxin,4.4 × 10⁻⁵Md-tubocurarine, or10⁻⁴M decamethonium. Atropine was only 50% effective at 10⁻⁴ M and hexamethonium was ineffective at 10⁻⁴ M.In vitro binding of receptor ligands to membranes prepared from TE671 cells revealed high levels of [¹²⁵I]α-bungarotoxin (α-BuTx) binding sites, in addition to lower levels of other ligand binding sites.[¹²⁵I]α-BuTx bound to a single, saturable high affinity site in either membrane preparations or intact TE671 cells. Binding was potently inhibited by the classical nicotinic acetylcholine receptor antagonistsd-tubocurarine and decamethonium. Nicotine and carbamylcholine showed intermediate potencies in inhibiting binding while atropine and hexamethonium showed little ability to inhibit [¹²⁵I]α-BuTx binding.The data obtained from [¹²⁵I]α-BuTx binding studies agree qualitatively with the electrophysiological data on the depolarizing ACh response and together they provide strong evidence that TE671 cells possess a functional nicotinic acetylcholine receptor. This cell line may therefore be useful as a stable source with which to characterize mammalian neuronal nicotinic acetylcholine receptors and membrane events related to its activation.     

Epibatidine binding sites and activity in the spinal cord

Epibatidine has been shown to be the most potent nicotinic agonist in several neuronal nicotinic receptor preparations. Similar to other nicotinic agonists, intrathecal (−)-epibatidine elicits dose-dependent increases in pressor, heart rate and pain responses in rats, as well as an increase in latency to withdraw from a noxious thermal stimulus. The latter response requires higher doses and is of shorter duration, suggesting interaction with multiple subtypes of spinal nicotinic receptors. In the present study, we relate the binding properties of (±)-[³H]epibatidine in spinal cord membrane preparations to the cardiovascular and behavioral responses. Unlike (−)-[³H]cytisine or (−)-[³H]nicotine, (±)-[³H]epibatidine reveals two sites; the ratio of high affinity to low affinity sites is 2:1. The rank ordering of potencies of the nicotinic agonists in displacing (±)-[³H]epibatidine binding from spinal cord membranes correlates with the potencies in eliciting cardiovascular and behavioral responses upon spinal administration. The nicotinic receptor antagonists, α-lobeline, dihydro-β-erythroidine and methyllycaconitine, also displayed similar rank ordering of potencies in displacing (±)-[³H]epibatidine, (−)-[³H]cytisine or (−)-[³H]nicotine binding to spinal nicotinic receptors. Virtually all the nicotinic analogs exhibited a Hill coefficient of less than one in competing with (±)-[³H]epibatidine to spinal cord membranes indicating their interaction with at least two classes of binding sites. Intrathecal (−)-epibatidine, in addition to eliciting an initial and subsequently a sustained pressor and tachycardic response, also exhibited a transient intervening bradycardia which coincided temporally with the duration of the analgesia. Repeated administration of (−)-epibatidine desensitized its responses as well as the cardiovascular and behavioral responses to spinal nicotine and cytisine. Intrathecal α-lobeline showed selectivity for blocking the analgesic response, whereas methyllycaconitine exhibited selectivity for the pressor and irritation responses. The NMDA receptor antagonist, AP-5, inhibited the pressor, tachycardic and irritation responses elicited by intrathecal (−)-epibatidine, confirming a role for spinal excitatory amino acids released by the nicotinic agonist. © 1997 Elsevier Science B.V. All rights reserved.     

α-Bungarotoxin blocks the nicotinic receptor mediated increase in cell number in a neuroendocrine cell line

Exposure of H69 small cell lung carcinoma cells to nicotinic agonists resulted in a significant increase (up to 100%) in cell number after 6 to 12 days. The effect of nicotine (10⁻⁸ M to 10⁻⁴ M) was both dose and time dependent as was that of another nicotinic agonist cytisine (10⁻⁶ M to 10⁻⁴ M). Interstingly, both the nicotine and cytisine induced increases in H69 cell number were blocked by α-bungarotoxin, as well as d-tubocurarine a nicotinic blocker which appears to interact with most nicotinic receptors. These results suggest that the nicotine induced increase in cell number is mediated through an interaction at the nicotinic α-bungarotoxin receptor. This idea is further supported by experiments which show (1) that H69 cells possess high affinity α-bungarotoxin sites (K_d = 25 nM, B_max = 10.4 fmol/10⁶ cells) with the characteristics of a nicotinic α-bungarotoxin receptor and (2) that the potencies of nicotinic receptor ligands in the α-bungarotoxin binding assay were similar to those observed in the functional studies. Northern analysis showed that mRNA for α7, a putative nicotinic α-bungarotoxin binding subunit, and for α5 were present in H69 cells. The present data provide further evidence that nicotine increases cell number in small cell lung carcinoma and are the first to show that this effect is mediated through an interaction at the nicotinic α-bungarotoxin receptor population. These results suggest that the α-bungarotoxin site may be involved in modulating proliferative responses in neuroendocrine derived SCLC cells.     

Thermogenic and corticosterone responses to intravenous cytokines (IL-1β and TNF-α) are attenuated by subdiaphragmatic vagotomy

The brain orchestrates changes in behavior and physiology as a consequence of peripheral immune activation and infection. These changes require that the brain receives signals from the periphery that an immunological challenge has occurred. Previous research has established that cytokines play a role in signalling the brain. What remains unclear, however, is how peripheral cytokines signal the central nervous system. A recent proposal is that cytokines signal the brain by stimulating peripheral nerves. The hypothesis states that following infection and the release of cytokines such as IL-1β into local tissue or microvasculature, IL-1β stimulates IL-1 receptors on vagal afferent terminals, or more likely on cells of vagal paraganglia. Vagal afferents, in turn, signal the brain. Previous work has demonstrated that transection of the vagus below the level of the diaphragm blocks or attenuates many illness consequences of intraperitoneally (i.p.) administered lipopolysaccharide (LPS) or IL-1β. The present studies extend these findings by examining the effect of subdiaphragmatic vagotomy on illness consequences following intravenously (i.v.) administered IL-1β and TNF-α. Subdiaphragmatic vagotomy attenuated both the fever response and corticosterone response produced by i.v. administered cytokines. This effect was dose dependent. The results add support to the hypothesis that vagal afferents are involved in peripheral cytokine-to-brain communication.     

Characterization of neuronal nicotinic receptors by snake venom neurotoxins

Neuronal nicotinic ACh receptors differ pharmacologically from nicotinic receptors on skeletal muscle. The use of certain snake venom neurotoxins has now led to a more complete determination of the pharmacological properties of these neuronal receptors, as well as to their ultrastructural localization. This review highlights results found using one such neurotoxin, toxin F, (also called bungarotoxin 3.1 and κ-bungarotoxin. Toxin F blocks nicotinic receptors in several neuronal preparations while having little affinity for nicotinic receptors in skeletal muscle. Autoradiographic studies using [¹²⁵I] toxin F indicate that nicotinic receptors in autonomic ganglia are clustered at synaptic sites, though their density is 3–30 times lower than that of nicotinic receptors at the neuromuscular junction.     

In vivo imaging of Α7 nicotinic receptors as a novel method to monitor neuroinflammation after cerebral ischemia

In vivo positron emission tomography (PET) imaging of nicotinic acetylcholine receptors (nAChRs) is a promising tool for the imaging evaluation of neurologic and neurodegenerative diseases. However, the role of α7 nAChRs after brain diseases such as cerebral ischemia and its involvement in inflammatory reaction is still largely unknown. In vivo and ex vivo evaluation of α7 nAChRs expression after transient middle cerebral artery occlusion (MCAO) was carried out using PET imaging with [¹¹C]NS14492 and immunohistochemistry (IHC). Pharmacological activation of α7 receptors was evaluated with magnetic resonance imaging (MRI), [¹⁸F]DPA‐714 PET, IHC, real time polymerase chain reaction (qPCR) and neurofunctional studies. In the ischemic territory, [¹¹C]NS14492 signal and IHC showed an expression increase of α7 receptors in microglia and astrocytes after cerebral ischemia. The role played by α7 receptors on neuroinflammation was supported by the decrease of [¹⁸F]DPA‐714 binding in ischemic rats treated with the α7 agonist PHA 568487 at day 7 after MCAO. Moreover, compared with non‐treated MCAO rats, PHA‐treated ischemic rats showed a significant reduction of the cerebral infarct volumes and an improvement of the neurologic outcome. PHA treatment significantly reduced the expression of leukocyte infiltration molecules in MCAO rats and in endothelial cells after in vitro ischemia. Despite that, the activation of α7 nAChR had no influence to the blood brain barrier (BBB) permeability measured by MRI. Taken together, these results suggest that the nicotinic α7 nAChRs play a key role in the inflammatory reaction and the leukocyte recruitment following cerebral ischemia in rats.     

Targeting ß2 adrenergic receptors regulate human T cell function directly and indirectly

It is well-established that central nervous system activation affects peripheral blood mononuclear cell (PBMCs) function through the release of the catecholamines (Epi) and norepinephrine (NE), which act on ß2-adrenergic receptors (ß2AR). However, most studies have used non-specific stimulation of cells rather than antigen-specific responses. Likewise, few studies have parsed out the direct effects of ß2AR stimulation on T cells versus indirect effects via adrenergic stimulation of antigen presenting cells (APC). Here we report the effect of salmeterol (Sal), a selective ß2AR agonist, on IFN-γ⁺ CD4 and IFN-γ⁺ CD8 T cells following stimulation with Cytomegalovirus lysate (CMVL-strain AD169) or individual peptides spanning the entire region of the HCMV pp65 protein (pp65). Cells were also stimulated with Staphylococcal enterotoxin B. Additionally, we investigated the effect of Epi and Sal on cytotoxic cell killing of transfected target cells at the single cell level using the CD107a assay.The results show that Sal reduced the percentage of IFN-γ⁺ CD4 and IFN-γ⁺ CD8 T cells both when applied directly to isolated T cells, and indirectly via treatment of APC. These inhibitory effects were mediated via a ß2 adrenergic-dependent pathway and were stronger for CD8 as compared to CD4 T cells. Similarly, the results show that Sal suppressed cytotoxicity of both CD8 T and NK cells in vitro following stimulation with Chinese hamster ovary cell line transfected with MICA^*009 (T-CHO) and the human erythromyeloblastoid leukemic (K562) cell line. The inhibitory effect on cytotoxicity following stimulation with T-CHO was stronger in NK cells compared with CD8 T cells.Thus, targeting the ß2AR on lymphocytes and on APC leads to inhibition of inflammatory cytokine production and target cell killing. Moreover, there is a hierarchy of responses, with CD8 T cells and NK cells inhibited more effectively than CD4 T cells.     

迷走神经切断对胃肠道给予大鼠伤寒杆菌诱发的下丘脑室旁核和视上核Fos表达的影响

为研究迷走神经在自然感染状态下向脑传递免疫信息的作用。应用免疫组织化学方法,观察了切断隔下迷走神经对大鼠消化道内给予鼠伤寒杆菌刺激诱发的下丘脑室旁核和视上核的Fos表达变化的影响。结果发现,接受细菌刺激的动物与仅给予生理盐水的动物相比,回肠和肠系膜淋巴结有明显炎症存在,室旁结果发现,接受细菌刺激的动物与仅给予生理盐水的动物相比,回肠和肠系膜淋巴结有明显炎症存在,室旁核外侧部和视上核背侧部的Fos阳性细胞数增加;膈下迷走神经切断后,手术 细菌组与假手术 细菌组相比,室旁核的外侧部和视上核背部Fos表达减少。因此迷走神经途径在自然感染性免疫应答过程中,特别是在其早期阶段可能是传递腹腔免疫信息的重要途径之一。     

Expression of α 7 neuronal nicotinic receptors during postnatal development of the rat cerebellum

Several lines of evidence suggest that α-bungarotoxin-sensitive neuronal nicotinic acetylcholine receptors may play a developmental role by modulating plasticity in neuronal circuits. The α7 subunit, a main component of these receptors, is expressed in most regions of the brain, including the cerebellum, where it is present almost exclusively in Purkinje cells and deep cerebellar nuclei. Purkinje cells constitute the only efferent pathway of the cerebellum and their development involves complex interactions, which have been extensively studied. They therefore provide a potentially useful model for analysis of developmental plasticity which could be influenced by α7 neuronal nicotinic receptors. In the present study a previously characterized monoclonal antibody (mAb 307) has been used to determine the temporal pattern of expression of the α7 subunit in the developing rat cerebellum. No detectable α7 immunoreactivity is found between P0 and P2. Between P3 and P5, however, the Purkinje cell layer shows moderate immunolabeling. α7 expression in this layer increases rapidly between P8 and P15. This increase in α7 staining, which overlaps in time with important developmental and synaptogenic events, is not uniform throughout the cerebellar cortex. Thus, between P3 and P5 all Purkinje cells are weakly labeled, while at later stages (P8–P15) immunolabeling becomes more intense but, at the same time, disappears from Purkinje cells in rostral lobules. In addition, a very well defined pattern of discontinuous or columnar labeling is detected in regions of the Purkinje cell layer where α7 subunits are being expressed. Finally, at P20, α7 subunit labeling is found again in all Purkinje cells, although with lower intensity. These results suggest that α7 receptor expression is developmentally regulated, with a time course that parallels the final differentiation of Purkinje cells. In addition, the heterogeneous spatial distribution of α7-containing nicotinic receptors indicates that, during cerebellar maturation, these cells may receive different signals that modulate receptor gene expression in a very specific way.     

Ibogaine acts at the nicotinic acetylcholine receptor to inhibit catecholamine release

In an effort to determine mechanisms of action of the putative anti-addictive agent ibogaine, we have measured its effects on catecholamine release in a model neuronal system, cultured bovine chromaffin cells. Various modes of stimulating catecholamine release were used including nicotinic ACh receptor activation, membrane depolarization with elevated K⁺ and Na⁺ channel activation with veratridine. In addition, because ibogaine has been reported to interact with kappa opioid receptors, we tested whether kappa receptor antagonists could reverse ibogaine's effects on catecholamine release. Ibogaine, at low concentration (<10 μM) was found to selectively inhibit nicotinic receptor-mediated catecholamine release, while having no significant effect on release evoked by either veratridine or membrane depolarization with elevated K⁺. The inhibitory actions of ibogaine and the kappa agonists were not reversed by preincubation with the opioid antagonists nor-binaltorphimine or naltrexone, suggesting that these inhibitory effects are not mediated by the kappa opioid receptor. The effects of low dose (10 μM) ibogaine were rapidly reversible, while the inhibitory effects of higher ibogaine doses persisted for at least 19 h following ibogaine washout. The results provide evidence for a mechanism of action ibogaine at the nicotinic ACh receptor. The results are consistent with a model in which the initial high transient brain concentrations (100 μM) of ibogaine act at multiple cellular sites and then have a selective action at the nicotinic ACh receptor cation channel following its metabolism to lower brain concentrations. The present findings are relevant to potential anti-addictive actions of ibogaine and to the development of drugs to combat nicotine addiction.     

Differential regulation of muscarinic and nicotinic receptors by cholinergic stimulation in cultured avian retina cells

Sustained cholinergic stimulation of retina cells grown in primary aggregate and monolayer cultures regulated the concentration of muscarinic but not nicotinic receptors. Muscarinic receptor sites, quantified by the binding of [³H]quinuclidinyl benzilate to membranes and the binding of [³H]N-methyl-scopolamine to intact cells, decreased up to 84% following long-term incubation of cultures in muscarinic agonists. This decrease was blocked by atropine and was not induced by chronic nicotine treatment. The rate of the muscarinic response was biphasic. A rapid binding decrease of 30% occurred within 15 min. The slower phase was half-maximal by 6 h and was complete by 24 h. Neither the fast nor the slow receptor loss was reversed by the guanine nucleotide GppNp. Three different depolarizing agents (gramicidin D, protoveratrine, and ouabain) blocked the cholinergic-induced receptor loss, but the hyperpolarizing ionophore valinomycin had no effect. In contrast to the muscarinic response, nicotinic receptor binding was not altered by chronic receptor stimulation. Exposure to receptor-saturating doses of carbamylcholine or nicotine for 48 h did not change [¹²⁵I]α-bungarotoxin or [³H]bromoacetylcholine binding. Differential regulation of acetylcholine receptors is discussed in relation to the possible physiological role of receptor regulation by receptor activity.     

Nicotine-induced release of noradrenaline from hypothalamic synaptosomes

In order to elucidate the functional role of nicotinic receptors in the hypothalamus, the drug-induced release of noradrenaline from hypothalamic synaptosomes was studied utilizing [³H] noradrenaline ([³H]NA). The release of [³H]NA from synaptosomes was significantly increased with an increase of the dose of nicotine, carbamylcholine chloride, reserpine or tyramine hydrochloride added to the medium, whereas arecoline, atropine sulfate or mecamylamine hydrochloride had no significant effect. Mecamylamine hydrochloride completely inhibited the nicotine- or carbamylcholine-induced release of [³H]NA at the concentration of 10⁻⁴ M, but had no effect on the reserpine- or tyramine-induced release of [³H]NA. A high concentration of potassium in the medium which depolarizes the synaptosome membrane significantly enhanced the release of [³H]NA. These results strongly suggest that there exist nicotinic cholinergic receptors in brain synaptic regions which play an important role in the function of hypothalamus by releasing noradrenaline and that the release mechanism of noradrenaline induced by nicotine is different from that induced by reserpine and tyramine. Although the existence of postsynaptic nicotinic receptor sites could not be ruled out, the present studies indicate the importance of presynaptic cholinergic receptors in the brain.     

A functional study of uncrossed and crossed pulmonary afferent fibres in the cervical vagus nerves of the cat

The functional distribution of uncrossed and crossed pulmonary afferent fibres in the cervical vagus nerves has been studied in the anaesthetized cat using acute and chronic unilateral pneumonectomized preparations. The heart and lungs were sympathectomized routinely. The vagal afferent pathways of three pulmonary reflexes were investigated: the Hering-Breuer respiratory reflex, the lung inflation cardio-accelerator reflex, and the pulmonary chemoreflex. Inflation of the remaining lung caused temporary inhibition of inspiration. It also resulted in acceleration of the heart, but only when the background cardiac vagal tone was augmented. These respiratory and cardiac responses were abolished in most animals by ipsilateral cervical vagotomy; however, in some, a small response persisted and this was abolished by contralateral vagotomy. Stimulation of pulmonary C-fibre endings with right atrial injections of phenylbiguanide caused a reduction in respiration, bradycardia and systemic hypotension, responses which occurred with a latency of 2.9 +/- 0.15 s. They were mostly abolished by ipsilateral cervical vagotomy, but reduced responses persisted in a few animals. The residual responses were abolished by contralateral cervical vagotomy and by selective denervation of the lung. These results indicate that most afferent fibres subserving the three pulmonary reflexes studied run in the ipsilateral cervical vagus, representing the uncrossed pathway. Some afferent fibres, however, cross to the contralateral cervical vagus. Degenerative changes in cells of the contralateral nodose ganglion in chronic unilateral pneumonectomized animals support these findings.     

Withdrawal and restoration of central vagal afferents within the dorsal vagal complex following subdiaphragmatic vagotomy

Vagotomy, a severing of the peripheral axons of the vagus nerve, has been extensively utilized to determine the role of vagal afferents in viscerosensory signaling. Vagotomy is also an unavoidable component of some bariatric surgeries. Although it is known that peripheral axons of the vagus nerve degenerate and then regenerate to a limited extent following vagotomy, very little is known about the response of central vagal afferents in the dorsal vagal complex to this type of damage. We tested the hypothesis that vagotomy results in the transient withdrawal of central vagal afferent terminals from their primary central target, the nucleus of the solitary tract (NTS). Sprague–Dawley rats underwent bilateral subdiaphragmatic vagotomy and were sacrificed 10, 30, or 60 days later. Plastic changes in vagal afferent fibers and synapses were investigated at the morphological and functional levels by using a combination of an anterograde tracer, synapse‐specific markers, and patch‐clamp electrophysiology in horizontal brain sections. Morphological data revealed that numbers of vagal afferent fibers and synapses in the NTS were significantly reduced 10 days following vagotomy and were restored to control levels by 30 days and 60 days, respectively. Electrophysiology revealed transient decreases in spontaneous glutamate release, glutamate release probability, and the number of primary afferent inputs. Our results demonstrate that subdiaphragmatic vagotomy triggers transient withdrawal and remodeling of central vagal afferent terminals in the NTS. The observed vagotomy‐induced plasticity within this key feeding center of the brain may be partially responsible for the response of bariatric patients following gastric bypass surgery. J. Comp. Neurol. 521:3584‐3599, 2013. © 2013 Wiley Periodicals, Inc.     

Axotomy alters neurotrophin and neurotrophin receptor mRNAs in the vagus nerve and nodose ganglion of the rat

Neurotrophins and neurotrophin receptors play an important role in survival and growth of injured peripheral nerves. To study the injury-mediated neurotrophic response in autonomic nerves, we investigated changes in mRNA expression of neurotrophins and their receptors in the transected vagus nerve and nodose ganglion. Studies using in situ hybridization histochemistry showed that axotomy of the cervical vagus nerve resulted in increased expression of mRNAs for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), and for TrkA, TrkB, and TrkC receptors in non-neuronal cells at both the proximal and distal segments of the transected cervical vagus nerve. Moreover, NGF protein was increased in the distal end, and NT-3 protein was increased in both the proximal and the distal ends of the transected nerve 3 days after axotomy. No change of p75(NTR) mRNA was detected in the transected vagus nerve. The induction of each neurotrophin and Trk receptor mRNA was apparent within 1 day after the axotomy and was sustained at least 14 days. By 45 days after the axotomy, a time when axonal reconnection with target tissue is made (integrity of the nerve-target connection was confirmed by the retrograde transport of FluoroGold from the stomach to vagal cell bodies), the levels of neurotrophin and Trk mRNAs in the vagus nerve declined to pre-axotomy levels. TrkA, TrkC, and p75(NTR) mRNA-containing vagal sensory neurons in the nodose ganglion were reduced in number after cervical vagotomy. Neurotrophin-mRNA-containing neurons were not found in the nodose ganglia from either intact or vagotomized rats. The axotomy-induced up-regulation of neurotrophins and Trk receptors mainly in the non-neuronal cells at or near the site of transection suggests that neurotrophins are involved in the survival and regeneration process of the vagus nerve after injury.     

Effects of afferent and efferent denervation of vagal nerve on endotoxin-induced oxidative stress in rats

This study investigated the role of vagal innervation in oxidative stress after systemic administration of lipopolysaccharide (LPS) endotoxin. Control rats and rats subjected to bilateral subdiaphragmatic vagotomy, perivagal capsaicin application (5 mg/ml) or cholinergic receptor blockade with subcutaneous atropine (1 mg/kg), were intraperitoneally injected with 300 μg/kg of LPS and euthanized 4 h later. Results indicated that; (1) surgical vagotomy and sensory denervation by perivagal capsaicin increased brain oxidative stress and decreased reduced glutathione in basal condition (saline-treated rats) and following endotoxin challenge; (2) oxidative stress decreased after cholinergic blockade with atropine in endotoxemic rats; (3) nitric oxide decreased by abdominal vagotomy, sensory deafferentation and cholinergic blockade after endotoxin injection; (4) liver lipid peroxidation decreased after surgical vagotomy and cholinergic blockade but increased after sensory deafferentation; (5) liver reduced glutathione decreased following vagotomy and sensory denervation in basal state and by cholinergic blockade in basal state and during endotoxemia; (6) nitric oxide increased by vagotomy in basal state and by sensory denervation and cholinergic blockade in basal state and during endotoxemia; (7) liver histological damage increased by subdiaphragmatic vagotomy, sensory denervation or cholinergic blockade. These findings suggest that: (1) sensory fibers (signals from the periphery) running in the vagus nerves are important in maintaining the redox status of the brain; (2) capsaicin vagal sensory nerves are likely to maintain nitric oxide tone in basal conditions; (3) the vagus nerve modulates liver redox status and nitric oxide release, (4) the vagus nerve mediates protective role in the liver with both cholinergic and capsaicin-sensitive mechanisms being involved.