Activation Of Cholinergic Receptors Research Articles

Abstract P213: Furosemide-mediated Suppression Of P 38 MAPK Signaling Abrogates Cholinergic-mediated Salt Sensitive Hypertension In Young Spontaneously Hypertensive Rats

Hypertension is a major cause of premature death worldwide. Inflammatory macrophages play a key role in the pathogenesis of hypertension. Our lab has observed that nicotinic acetylcholine receptors (nAChR) activation potentiates salt-sensitive hypertension in Spontaneously Hypertensive Rats (SHR). Cholinergic receptor activation causes infiltration of CD68 + macrophages into the renal cortex/medulla junction and results in enhanced expression of renal sodium-potassium chloride cotransporter (NKCC2). To determine whether or not NKCC2 plays a role in the activation of inflammatory pathway furosemide, a selective pharmacologic blocker of NKCC2, was used to block NKCC2 expression in SHR in current study. Young pre-hypertensive SHR, receiving nicotine infusion (15mg/kg/day), were fed HSD (4% NaCl) and treated with either saline or furosemide (20mg/kg/day) intraperitoneal injections. There was a 16% increase (158.5±7.3 mmHg to 183.6±7.0 mmHg) in the systolic blood pressure in SHR that received saline injections, compared to no increase in SHR that received furosemide (155±6.0 mmHg to 148±3.6 mmHg) (p<0.0016). There was over a two-fold increase in fractional excretion of sodium (FENa, p=0.03) in the furosemide group, compared to saline controls. Although furosemide injections did not alter renal NKCC2 expression, there was nearly 50% reduction in phosphorylated p38 MAPK (p=0.0002) and a 25% decrease in renal infiltration of inflammatory CD68 + macrophages in SHR receiving furosemide injections, compared to saline controls. Interestingly, there was also a significant reduction in urinary albumin in response to furosemide injections (14.7±5.7 control vs 3.3±0.9 furosemide, p=0.027). Based on these findings, we conclude that furosemide results in cessation of the development of hypertension via interruption of a p38-MAPK dependent inflammatory pathway.

The involvement of the central cholinergic system in the hyperventilation effect of centrally injected nesfatin-1 in rats

We recently demonstrated that peripheral and central administration of nesfatin-1 in fasting and satiety states generate hyperventilation activity by increasing tidal volume (TV), respiratory rate (RR), and respiratory minute ventilation (RVM). The present study aimed to investigate the mediation of central cholinergic receptors effective in respiratory control in the hyperventilation activity of nesfatin-1. Besides this, we intended to determine possible changes in blood gases due to hyperventilation activity caused by nesfatin-1 and investigate the mediation of central cholinergic receptors in these changes.Intracerebroventricular (ICV) administration of nesfatin-1 revealed a hyperventilation response with an increase in TV, RR, RMV, and pO2 and a decrease in pCO2 in saturated Sprague Dawley rats. ICV pretreatment with the muscarinic receptor antagonist atropine partially blocked the RR, RMV, pO2, and pCO2 responses produced by nesfatin-1 while completely blocking the TV response. However, central pretreatment with nicotinic receptor antagonist mecamylamine blocked the respiratory and blood gas responses induced by nesfatin-1.The study's conclusion demonstrated that nesfatin-1 had active hyperventilation effects resulting in an increase in pO2 and a decrease in pCO2. The critical finding of the study was that activation of central cholinergic receptors was involved in nesfatin-1-evoked hyperventilation and blood gas responses.

Pay attention to the reversible changes of anesthetics and postoperative cognitive dysfunction.

The progress of human civilization and the development in the new era have put forward higher-level demands for medical industry. The enhancement of health awareness and the improvement of diagnosis and treatment methods have promoted the development of comfortable medicine. Anesthesiologists play such an important role in perioperative period and the comfortable medicine. Evidences show that the diagnosis and treatment of anesthesiologists enable patients to recover quickly, improve treatments, save money, reduce family and social burdens. Postoperative cognitive dysfunction is one of the most common problems faced in perioperative medicine. Although postoperative cognitive dysfunction isn’t a direct threat for life, it may reduce the degree of medical cooperation, occur adverse events unnecessarily, prolong hospital stay, increase expenses and the anxiety of patients and other negative effects. Therefore, clarifying the risk factors of postoperative cognitive dysfunction and exploring effective medical methods are necessary to solve the above problems. The Anesthesiology Branch of the Chinese Medical Association has established a special group for the research of postoperative cognitive dysfunction. At present, research teams in China have been committed to related research on postoperative cognitive dysfunction for a long time. Many results provided valuable suggestions for the prevention and treatment of cognitive dysfunction. Studies showed that age and coronary artery bypass grafting and other major operations are important risk factors for postoperative cognitive dysfunction. This provides warnings for the prevention of postoperative cognitive function in clinical diagnosis and treatment. The management of specific populations and types of surgery are necessary for anesthesiologists to carry out early psychological construction, humanistic care and even medical intervention for patients in particular. Another important finding in these studies is that the occurrence of postoperative cognitive dysfunction is reversible, and the risk period is mainly the early postoperative period and barely has a serious impact on the long-term cognition. These results point out the direction for further improvement of perioperative medicine. With the development of the western region of China, the team of Professor Zhao-Qiong Zhu from the Affiliated Hospital of Zunyi Medical University committed a lot for years in the field of postoperative cognitive dysfunction. The research team found that patients with postoperative cognitive dysfunction are mainly elderly people in clinical studies, and this phenomenon is reversible, and mainly happened in 1 week after surgery. It rarely lasts for months or years. This provides an important theoretical basis to explain the occurrence of this phenomenon and diagnosis as same as provide treatment timely in clinic. On this basis, the team of Professor Zhao-Qiong Zhu carried out further research from the perspectives of behavior, molecular biology, cell biology, morphology, imaging, etc. in order to ascertain the relevant mechanism of postoperative cognitive dysfunction. The results also revealed that the behavioral effects of inhalation anesthetics on experimental animals at clinical and subclinical concentrations are only limited to the early stage after drug application, and the related mechanism may be related to the activation of inflammasomes and central cholinergic receptors. The series of researches provide valuable suggestions for rationally explaining the occurrence of postoperative cognitive dysfunction in clinical diagnosis as well as treatment and further research for postoperative cognitive dysfunction in the future. With the improvement of living standards, the demand for health increases for people. The reversible changes of postoperative cognitive dysfunction as one of the key medical problems in the world will cause concerns for scholars committed to solving. With the efforts of diligent researchers, it is bound to promote the development of medicine.

The Non‐Neuronal Cholinergic System is Causal for Cardioprotection by Hypoxic Preconditioning in Isolated Adult Rat Cardiomyocytes

Introduction Brief episodes of non-lethal myocardial ischemia/reperfusion preceding more sustained ischemia reduce lethal ischemia/reperfusion injury in all species tested so far, including humans. Although this phenomenon is known for more than 3 decades, the underlying signaling mechanisms are unclear in their details. Among various cardioprotective mediators, neuronal acetylcholine (ACh) and its signaling through cholinergic receptors is certainly involved. However, a non-neuronal cardiac cholinergic system (NNCCS) has been recently identified, suggesting a nervous system-independent, cardiomyocyte-derived ACh signaling with signal amplification by autocrine cholinergic receptor activation. Aim We aimed to examine the role of NNCCS-derived ACh as a mediator of cardioprotection. We therefore in a reductionist approach used isolated adult cardiomyocytes with hypoxic preconditioning (HPC). Methods Hearts from male Lewis rats were harvested, and adult ventricular cardiomyocytes were isolated. In suspended cardiomyocytes HPC was induced by one cycle of 10 min brief hypoxia and 20 min reoxygenation. Thirty min normoxia served as control. Afterwards, cardiomyocytes were exposed to 30 min sustained hypoxia and 5 min reoxygenation (H/R) or to 35 min normoxia as time control (TC). Cardiomyocyte viability was quantified before and after H/R or TC, respectively, as the percent fraction of rod-shaped, unstained (0.5% trypan blue) cells over all cells. In parallel experiments, physostigmine (0.2 mmol/L) was added to cardiomyocyte suspensions to block the ubiquitous ACh esterase. Intracellular ACh was quantified with and without HPC via liquid chromatography-coupled tandem mass spectrometry. In subsets, the nicotinic cholinergic receptor antagonists hexamethonium (1.0 µmol/L) and α-bungarotoxine (0.1 µmol/L) or the muscarinic cholinergic receptor antagonist atropine (0.1 µmol/L) were added to cardiomyocyte suspensions with and without HPC, respectively, and exposure to H/R or TC, respectively, afterwards. Again, cardiomyocyte viability was quantified. Results With HPC, the viability of cardiomyocytes subjected to H/R was better preserved than without (24±1% vs. 7±1%, figure A). Also, intracellular ACh was slightly (n.s.) increased after sustained hypoxia (6±2 pmol/mg protein), but significantly with HPC (13±3 pmol/mg protein) in comparison to baseline (3±1 pmol/mg protein) or TC (3±1 pmol/mg protein, figure B). However, this increase was only detectable in the presence of physostigmine (figure B). Addition of nicotinic and muscarinic cholinergic receptor antagonists attenuated the protection by HPC to the same extent (hexamethonium: 12±2%, α-bungarotoxine: 11±1%, atropine: 10±1%, figure A). Conclusion The NNCCS is activated by HPC and causal for HPC´s protection. HPC increases intracellular ACh, and cardiomyocyte protection is mediated via both nicotinic and muscarinic cholinergic receptors, suggesting an autocrine signal amplification on the cardiomyocyte level.

Noradrenergic Suppression of Persistent Firing in Hippocampal CA1 Pyramidal Cells through cAMP-PKA Pathway.

Persistent firing is believed to be a cellular correlate of working memory. While the effects of noradrenaline (NA) on working memory have widely been described, its effect on the cellular mechanisms of persistent firing remains largely unknown. Using in vitro intracellular recordings, we demonstrate that persistent firing is supported by individual neurons in hippocampal CA1 pyramidal cells through cholinergic receptor activation, but is dramatically attenuated by NA. In contrast to the classical theory that recurrent synaptic excitation supports persistent firing, suppression of persistent firing by NA was independent of synaptic transmission, indicating that the mechanism is intrinsic to individual cells. In agreement with detrimental effects of cAMP on working memory, we demonstrate that the suppressive effect of NA was through cAMP-PKA pathway. In addition, activation of β1 and/or β3 adrenergic receptors, which increases cAMP levels, suppressed persistent firing. These results are in line with working memory decline observed during high levels of NA and cAMP, which are implicated in high stress, aging, and schizophrenia.

Exposure System Dependent Calcium Influx in Chromaffin Cells by Nanosecond Electric Pulse- Field Reflections at Dielectric Interface

Nanosecond electric pulses have been successfully used as a novel electrical stimulus for evoking a dependent catecholamine release from the bovine adrenal chromaffin cells. It was observed that the duration of calcium influx varies depending on the exposure system. For example, cells exposed to 5 ns and 5MV/m pulses by a gold strip exposure chamber elicited calcium responses similar to the physiological stimulus, nicotinic cholinergic receptor activation. On the other hand, recent exposure systems utilizing tungsten rod electrodes evoke an undesired calcium response that is relatively long-lived even by exposure of the same pulse.

Neuronal localization of m1 muscarinic receptor immunoreactivity in the monkey basolateral amygdala.

The basolateral nuclear complex (BNC) of the amygdala plays an important role in the generation of emotional/motivational behavior and the consolidation of emotional memories. Activation of M1 cholinergic receptors (M1Rs) in the BNC is critical for memory consolidation. Previous receptor binding studies in the monkey amygdala demonstrated that the BNC has a high density of M1Rs, but did not have sufficient resolution to identify which neurons in the BNC expressed them. This was accomplished in the present immunohistochemical investigation using an antibody for the m1 receptor (m1R). Analysis of m1Rs in the monkey BNC using immunoperoxidase techniques revealed that their expression was very dense in the BNC, and suggested that virtually all of the pyramidal projection neurons (PNs) in all of the BNC nuclei were m1R-immunoreactive (m1R+). This was confirmed with dual-labeling immunofluorescence using staining for calcium/calmodulin-dependent protein kinase II (CaMK) as a marker for BNC PNs. However, additional dual-labeling studies indicated that one-third of inhibitory interneurons (INs) expressing glutamic acid decarboxylase (GAD) were also m1R+. Moreover, the finding that 60% of parvalbumin (PV) immunoreactive neurons were m1R+ indicated that this IN subpopulation was the main GAD+ subpopulation exhibiting m1R expression. The cholinergic innervation of the amygdala is greatly reduced in Alzheimer's disease and there is currently considerable interest in developing selective M1R positive allosteric modulators (PAMs) to treat the symptoms. The results of the present study indicate that M1Rs in both PNs and INs in the primate BNC would be targeted by M1R PAMs.

Cholinergic receptors play a role in the cardioprotective effects of anesthetic preconditioning: Roles of nitric oxide and the CaMKKβ/AMPK pathway.

Vagus nerve activation may have important therapeutic significance for myocardial ischemia-reperfusion (IR) injury. Nitric oxide (NO) plays a vital role in the cardioprotective effects of anesthetic preconditioning (APC). Moreover, acetylcholine (ACh) prevents cardiomyocyte damage by activating AMP-activated protein kinase (AMPK) and increasing the phosphorylation of Ca2+/calmodulin-dependent protein kinase β (CaMKKβ). The aim of the present study was to determine whether APC could protect heart function by antagonizing IR damage via the cholinergic system. It was hypothesized that the NO synthase (NOS)/CaMKKβ/AMPK pathway might be involved in the cardioprotective effects induced by cholinergic receptor activation. Isolated rat hearts were subjected to ischemia for 30 min followed by 120 min of reperfusion. Volatile anesthetic sevoflurane (3.5%) was administered for 15 min before ischemia, then rinsed for 15 min. The muscarinic acetylcholine receptor (mAChR) antagonist atropine (ATR; 100 nM) and the nicotinic acetylcholine receptor (nAChR) antagonist hexamethonium (HEM; 50 µM) were administered 10 min before APC. Both mAChR and nAChR were involved in APC-induced cardioprotection. ATR and HEM treatment both abolished the protective effects of APC on IR damage in isolated hearts, demonstrating the importance of cholinergic receptors in the protection mechanism of APC. The present study thus suggests that APC plays a cardioprotective role, in part, by regulating neurohumoral pathways. In addition, there may be functional coupling between the two cholinergic receptors, and the NOS and CaMKKβ/AMPK pathways may play roles in shared pathways that mediate the cardioprotective effects of APC. These findings may provide insight into potential new mechanisms of APC-induced cardioprotection against IR injury.

Neuronal innervation of the intestinal crypt.

Mucosal damage is a key feature of inflammatory bowel diseases (IBD) and healing of the mucosa is an endpoint of IBD treatment that is often difficult to achieve. Autonomic neurons of the parasympathetic and sympathetic nervous system may influence intestinal epithelial cell growth and modulating epithelial innervation could for that reason serve as an interesting therapeutic option to improve mucosal healing. Understanding of the biological processes triggered by nonspecific and specific epithelial adrenergic and cholinergic receptor activation is of key importance. At present, with rising technological advances, bioelectronic neuromodulation as treatment modality has gained momentum. We discuss the current view on state-of-the-art innervation of the intestinal crypt and its impact on epithelial cell growth and differentiation. Furthermore, we outline bioelectronic technology and review its relevance to wound healing processes.

Experience enhances certainty about olfactory stimuli under bulbar cholinergic control.

We present evidence that experience and cholinergic modulation in an early sensory network interact to improve certainty about olfactory stimuli. The data we present are in agreement with existing theoretical ideas about the functional role of acetylcholine but highlight the importance of early sensory networks in addition to cortical networks. We use a simple behavioral paradigm in mice which allows us to measure certainty about a stimulus via the response amplitude to a condition and novel stimuli. We conclude that additional learning increases certainty and that the slope of this relationship can be modulated by activation of muscarinic cholinergic receptors in the olfactory bulb.

Lactate Attenuates Synaptic Transmission and Affects Brain Rhythms Featuring High Energy Expenditure.

SummaryLactate shuttled from blood, astrocytes, and/or oligodendrocytes may serve as the major glucose alternative in brain energy metabolism. However, its effectiveness in fueling neuronal information processing underlying complex cortex functions like perception and memory is unclear. We show that sole lactate disturbs electrical gamma and theta-gamma oscillations in hippocampal networks by either attenuation or neural bursts. Bursting is suppressed by elevating the glucose fraction in substrate supply. By contrast, lactate does not affect electrical sharp wave-ripple activity featuring lower energy use. Lactate increases the oxygen consumption during the network states, reflecting enhanced oxidative ATP synthesis in mitochondria. Finally, lactate attenuates synaptic transmission in excitatory pyramidal cells and fast-spiking, inhibitory interneurons by reduced neurotransmitter release from presynaptic terminals, whereas action potential generation in the axon is regular. In conclusion, sole lactate is less effective and potentially harmful during gamma-band rhythms by omitting obligatory ATP delivery through fast glycolysis at the synapse.

Genome-wide microRNA profiling in brain and blood samples in a mouse model of epileptogenesis

ObjectivesThis study profiled circulating and hippocampal microRNAs (miRNAs) to identify alterations associated with the risk of epileptogenesis in a mouse temporal lobe epilepsy model. MethodsNext-generation sequencing was performed to examine the changes in miRNA expression 24 h after pilocarpine-induced status epilepticus (SE) in C57BL/6NCrl mice using both blood and hippocampus samples. Differentially expressed miRNAs were identified from SE animals and matched controls that failed to develop SE after receiving equal doses of pilocarpine (NS animals). Blood and brain miRNA profiles were then compared to identify circulating miRNA alterations reflecting the changes in the brain. ResultsWe identified 3 miRNAs that were significantly up-regulated and 4 miRNAs that were significantly down-regulated in the blood of SE animals compared with NS animals. When hippocampal miRNAs of SE animals and NS animals were compared, 5 miRNAs were up-regulated and 4 were down-regulated. Of these, miR-434-3p and miR-133a-3p were observed to have greatest changes in both blood and brain of SE animals. SignificanceThis study extends current knowledge of changes in miRNAs associated with epileptogenesis by profiling miRNAs in SE and NS animals in an experimental temporal lobe epilepsy model. The study was designed to allow non-specific changes due to the activation of muscarinic cholinergic receptors in peripheral organs by pilocarpine to be ruled out. Significantly altered circulating miRNAs that reflect changes in the brain during epileptogenesis after SE have the potential to be developed as prognostic biomarkers for epileptogenesis.

Activation of a non‐neuronal cholinergic system in rat cardiomyocytes by cardioprotective humoral factors from pigs with remote ischemic conditioning

IntroductionBrief cycles of ischemia/reperfusion (I/R) in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) reduce myocardial I/R injury. Although operative in all species tested so far, including humans, the translation of RIC into clinical practice has been largely disappointing. Such failure in translation has in part been attributed to incomplete understanding of RIC’s signal transduction. RIC’s cardioprotection can be transferred with plasma between different individuals, even across species. Prior studies have suggested that the intrinsic nervous system is causally involved in RIC’s protection, since the ganglionic blocker hexamethonium attenuated the infarct size reduction in isolated rat hearts in response to plasma taken from different rats after RIC. However, recently a non‐neuronal cardiomyocyte‐based cholinergic system (NNCS) has been identified, and its involvement in the signal transduction of RIC is entirely unclear.We therefor aimed to study whether the NNCS is activated by humoral factor(s) released by RIC.MethodsAnesthetized open‐chest minipigs were subjected to 60/180 min occlusion/reperfusion of the left anterior descending coronary artery (n=7, placebo, PLA). RIC was induced by 4×5/5 min hindlimb I/R (n=8) 90 min before coronary occlusion. Arterial blood was sampled after PLA/RIC and plasma separated. Rat ventricular cardiomyocytes were isolated and incubated with PLA or RIC plasma‐dialysate (1:10; cut‐off <12–14 kDa) for 30 min ± hexamethonium (1 μmol/L) or ± atropine (100 nmol/L), respectively, subjected to 30/5 min hypoxia/reoxygenation (H/R) and compared to cardiomyocytes exposed to normoxic buffer (time control, TC) for 35 min. Cardiomyocyte viability was quantified before and after H/R or TC, respectively, as the percent fraction of rod‐shaped, unstained (trypan blue) cells over all cells. Diluted (1:10) PLA or RIC plasma was also infused into isolated perfused rat hearts for 8 min before 30/120 min global ischemia/reperfusion (GI/R) ± hexamethonium (50 μmol/L) or ± atropine (100 nmol/L), respectively. Infarct size (IS) was demarcated by triphenyltetrazolium chloride and calculated as percent of ventricular mass.ResultsIncubation with RIC plasma‐dialysate preserved cardiomyocyte viability after H/R in comparison to PLA plasma‐dialysate. This protection was attenuated by hexamethonium and by atropine. Hexamethonium or atropine had no impact on cardiomyocyte viability per se (Figure A). In isolated hearts, IS was less with infusion of plasma from pigs with RIC than with that from pigs with PLA. With infusion of PLA plasma, hexamethonium or atropine did not impact on IS per se. The protective effect of RIC plasma, however, was abrogated by hexamethonium and by atropine (Figure B).ConclusionRIC’s humoral transfer of cardioprotection is mediated via an activation of cholinergic receptors on cardiomyocytes and attenuated to the same extent by hexamethonium or by atropine. Whether or not hexamethonium also and additionally attenuates the cardioprotection of RIC at the ganglionic level therefore remains unclear.Support or Funding InformationSupported by the German Research Foundation (SFB 1116 B8)Figure legend: A) Viability of rat ventricular cardiomyocytes incubated with placebo (PLA)/remote ischemic conditioning (RIC) plasma‐dialysate after hypoxia (H)/reoxygenation(R), or after normoxic time control (TC). Cardiomyocytes with plasma‐dialysate were incubated with saline, ± hexamethonium (hexa), or ± atropine. Data are means ± standard deviations. †p<0.05 vs. PLA plasma‐dialysate; ‡p<0.05 vs. saline RIC plasma‐dialysate; two‐way ANOVA with Fisher’s least significant differences post‐hoc tests. B) Infarct size in isolated perfused rat hearts (± hexa or ± atropine) with infusion of PLA or RIC plasma and after global ischemia/reperfusion. Data are means ± standard deviations. #p<0.05 vs. PLA plasma; *p<0.05 vs. saline RIC plasma; two‐way ANOVA with Fisher’s least significant differences post‐hoc tests.Figure 1

The mechanisms shaping CA2 pyramidal neuron action potential bursting induced by muscarinic acetylcholine receptor activation.

Recent studies have revealed that hippocampal area CA2 plays an important role in hippocampal network function. Disruption of this region has been implicated in neuropsychiatric disorders. It is well appreciated that cholinergic input to the hippocampus plays an important role in learning and memory. While the effect of elevated cholinergic tone has been well studied in areas CA1 and CA3, it remains unclear how changes in cholinergic tone impact synaptic transmission and the intrinsic properties of neurons in area CA2. In this study, we applied the cholinergic agonist carbachol and performed on-cell, whole-cell, and extracellular recordings in area CA2. We observed that under conditions of high cholinergic tone, CA2 pyramidal neurons depolarized and rhythmically fired bursts of action potentials. This depolarization depended on the activation of M1 and M3 cholinergic receptors. Furthermore, we examined how the intrinsic properties and action-potential firing were altered in CA2 pyramidal neurons treated with 10 µM carbachol. While this intrinsic burst firing persisted in the absence of synaptic transmission, bursts were shaped by synaptic inputs in the intact network. We found that both excitatory and inhibitory synaptic transmission were reduced upon carbachol treatment. Finally, we examined the contribution of different channels to the cholinergic-induced changes in neuronal properties. We found that a conductance from Kv7 channels partially contributed to carbachol-induced changes in resting membrane potential and membrane resistance. We also found that D-type potassium currents contributed to controlling several properties of the bursts, including firing rate and burst kinetics. Furthermore, we determined that T-type calcium channels and small conductance calcium-activated potassium channels play a role in regulating bursting activity.

Post-treatment with Posiphen Reduces Endoplasmic Reticulum Stress and Neurodegeneration in Stroke Brain.

SummaryAcetylcholinesterase (AChE) inhibitors have protective and anti-inflammatory actions against brain injury, mediated by nicotinic α7 cholinergic receptor activation. The use of AChE inhibitors in patients is limited by systemic cholinergic side effects. Posiphen, a stereoisomer of the AChE inhibitor Phenserine, lacks AChE inhibitor activity. The purpose of this study is to determine the protective effect of Posiphen in cellular and animal models of stroke. Both Posiphen and Phenserine reduced glutamate-mediated neuronal loss in co-cultures of primary cortical cells and microglia. Phenserine-, but not Posiphen-, mediated neuroprotection was diminished by the nicotinic α7 receptor antagonist methyllycaconitine. Posiphen antagonized NMDA-mediated Ca++ influx, thapsigargin-mediated neuronal loss and ER stress in cultured cells. Early post-treatment with Posiphen reduced ER stress signals, IBA1 immunoreactivity, TUNEL and infarction in the ischemic cortex, as well as neurological deficits in stroke rats. These findings indicate that Posiphen is neuroprotective against stroke through regulating Ca++i and ER stress.

VIP and muscarinic synergistic mucin secretion by salivary mucous cells is mediated by enhanced PKC activity via VIP-induced release of an intracellular Ca2+ pool

Mucin secretion by salivary mucous glands is mediated predominantly by parasympathetic acetylcholine activation of cholinergic muscarinic receptors via increased intracellular free calcium ([Ca2+]i) and activation of conventional protein kinase C isozymes (cPKC). However, the parasympathetic co-neurotransmitter, vasoactive intestinal peptide (VIP), also initiates secretion, but to a lesser extent. In the present study, cross talk between VIP- and muscarinic-induced mucin secretion was investigated using isolated rat sublingual tubuloacini. VIP-induced secretion is mediated by cAMP-activated protein kinase A (PKA), independently of increased [Ca2+]i. Synergistic secretion between VIP and the muscarinic agonist, carbachol, was demonstrated but only with submaximal carbachol. Carbachol has no effect on cAMP ± VIP. Instead, PKA activated by VIP releases Ca2+ from an intracellular pool maintained by the sarco/endoplasmic reticulum Ca2+-ATPase pump. Calcium release was independent of phospholipase C activity. The resultant sustained [Ca2+]i increase is additive to submaximal, but not maximal carbachol-induced [Ca2+]i. Synergistic mucin secretion was mimicked by VIP plus either phorbol 12-myristate 13-acetate or 0.01μM thapsigargin, and blocked by the PKC inhibitor, Gö6976. VIP-induced Ca2+ release also promoted store-operated Ca2+ entry. Synergism is therefore driven by VIP-mediated [Ca2+]i augmenting cPKC activity to enhance muscarinic mucin secretion. Additional data suggest ryanodine receptors control VIP/PKA-mediated Ca2+ release from a Ca2+ pool also responsive to maximal carbachol. A working model of muscarinic and VIP control of mucous cell exocrine secretion is presented. Results are discussed in relation to synergistic mechanisms in other secretory cells, and the physiological and therapeutic significance of VIP/muscarinic synergism controlling salivary mucous cell exocrine secretion.

Muscarinic acetylcholine receptor-dependent persistent activity of layer 5 intrinsic-bursting and regular-spiking neurons in primary auditory cortex.

Cholinergic signaling coupled to sensory-driven neuronal depolarization is essential for modulating lasting changes in deep-layer neural excitability and experience-dependent plasticity in the primary auditory cortex. However, the underlying cellular mechanism(s) associated with coincident cholinergic receptor activation and neuronal depolarization of deep-layer cortical neurons remains unknown. Using in vitro whole cell patch-clamp recordings targeted to neurons (n = 151) in isolated brain slices containing the primary auditory cortex (AI), we investigated the effects of cholinergic receptor activation and neuronal depolarization on the electrophysiological properties of AI layer 5 intrinsic-bursting and regular-spiking neurons. Bath application of carbachol (5 µM; cholinergic receptor agonist) paired with suprathreshold intracellular depolarization led to persistent activity in these neurons. Persistent activity may involve similar cellular mechanisms and be generated intrinsically in both intrinsic-bursting and regular-spiking neurons given that it 1) persisted under the blockade of ionotropic glutamatergic (kynurenic acid, 2 mM) and GABAergic receptors (picrotoxin, 100 µM), 2) was fully blocked by both atropine (10 µM; nonselective muscarinic antagonist) and flufenamic acid [100 µM; nonspecific Ca2+-sensitive cationic channel (CAN) blocker], and 3) was sensitive to the voltage-gated Ca2+ channel blocker nifedipine (50 µM) and Ca2+-free artificial cerebrospinal fluid. Together, our results support a model through which coincident activation of AI layer 5 neuron muscarinic receptors and suprathreshold activation can lead to sustained changes in layer 5 excitability, providing new insight into the possible role of a calcium-CAN-dependent cholinergic mechanism of AI cortical plasticity. These findings also indicate that distinct streams of auditory processing in layer 5 intrinsic-bursting and regular-spiking neurons may run in parallel during learning-induced auditory plasticity.NEW & NOTEWORTHY Cholinergic signaling coupled to sensory-driven neuronal depolarization is essential for modulating lasting changes in experience-dependent plasticity in the primary auditory cortex. Cholinergic activation together with cellular depolarization can lead to persistent activity in both intrinsic-bursting and regular-spiking layer 5 pyramidal neurons. A similar mechanism involving muscarinic acetylcholine receptor, voltage-gated Ca2+ channel, and possible Ca2+-sensitive nonspecific cationic channel activation provides new insight into our understanding of the cellular mechanisms that govern learning-induced auditory cortical and subcortical plasticity.

Antinociceptive Activity of Petroleum Ether Fraction of Clinacanthus nutans Leaves Methanolic Extract: Roles of Nonopioid Pain Modulatory Systems and Potassium Channels.

Methanolic extract of Clinacanthus nutans Lindau leaves (MECN) has been reported to exert antinociceptive activity. The present study aimed to elucidate the possible antinociceptive mechanisms of a lipid-soluble fraction of MECN, which was obtained after sequential extraction in petroleum ether. The petroleum ether fraction of C. nutans (PECN), administered orally to mice, was (i) subjected to capsaicin-, glutamate-, phorbol 12-myristate 13-acetate-, bradykinin-induced nociception model; (ii) prechallenged (intraperitoneal (i.p.)) with 0.15 mg/kg yohimbine, 1 mg/kg pindolol, 3 mg/kg caffeine, 0.2 mg/kg haloperidol, or 10 mg/kg atropine, which were the respective antagonist of α2-adrenergic, β-adrenergic, adenosinergic, dopaminergic, or muscarinic receptors; and (iii) prechallenged (i.p.) with 10 mg/kg glibenclamide, 0.04 mg/kg apamin, 0.02 mg/kg charybdotoxin, or 4 mg/kg tetraethylammonium chloride, which were the respective inhibitor of ATP sensitive-, small conductance Ca2+-activated-, large conductance Ca2+-activated-, or nonselective voltage-activated-K+ channel. Results obtained demonstrated that PECN (100, 250, and 500 mg/kg) significantly (P<0.05) inhibited all models of nociception described earlier. The antinociceptive activity of 500 mg/kg PECN was significantly (P<0.05) attenuated when prechallenged with all antagonists or K+ channel blockers. However, only pretreatment with apamin and charybdotoxin caused full inhibition of PECN-induced antinociception. The rest of the K+ channel blockers and all antagonists caused only partial inhibition of PECN antinociception, respectively. Analyses on PECN's phytoconstituents revealed the presence of antinociceptive-bearing bioactive compounds of volatile (i.e., derivatives of γ–tocopherol, α–tocopherol, and lupeol) and nonvolatile (i.e., cinnamic acid) nature. In conclusion, PECN exerts a non-opioid-mediated antinociceptive activity involving mainly activation of adenosinergic and cholinergic receptors or small- and large-conductance Ca2+-activated-K+ channels.

Renal denervation and CD161a immune ablation prevent cholinergic hypertension and renal sodium retention

Cholinergic receptor activation leads to premature development of hypertension and infiltration of proinflammatory CD161a+/CD68+ M1 macrophages into the renal medulla. Renal inflammation is implicated in renal sodium retention and the development of hypertension. Renal denervation is known to decrease renal inflammation. The objective of this study was to determine the role of CD161a+/CD68+ macrophages and renal sympathetic nerves in cholinergic-hypertension and renal sodium retention. Bilateral renal nerve denervation (RND) and immune ablation of CD161a+ immune cells were performed in young prehypertensive spontaneously hypertensive rat (SHR) followed by infusion of either saline or nicotine (15 mg·kg-1·day-1) for 2 wk. Immune ablation was conducted by injection of unconjugated azide-free antibody targeting rat CD161a+. Blood pressure was monitored by tail cuff plethysmography. Tissues were harvested at the end of infusion. Nicotine induced premature hypertension, renal expression of the sodium-potassium chloride cotransporter (NKCC2), increases in renal sodium retention, and infiltration of CD161a+/CD68+ macrophages into the renal medulla. All of these effects were abrogated by RND and ablation of CD161a+ immune cells. Cholinergic activation of CD161a+ immune cells with nicotine leads to the premature development of hypertension in SHR. The effects of renal sympathetic nerves on chemotaxis of CD161a+ macrophages to the renal medulla, increased renal expression of NKCC2, and renal sodium retention contribute to cholinergic hypertension. The CD161a+ immune cells are necessary and essential for this prohypertensive nicotine-mediated inflammatory response.NEW & NOTEWORTHY This is the first study that describes a novel integrative physiological interaction between the adrenergic, cholinergic, and renal systems in the development of hypertension, describing data for the role of each in a genetic model of essential hypertension. Noteworthy findings include the prevention of nicotine-mediated hypertension following successful immune ablation of CD161a+ immune cells and the necessary role these cells play in the overexpression of the sodium-potassium-chloride cotransporter (NKCC2) in the renal medulla and renal sodium retention. Renal infiltration of these cells is demonstrated to be dependent on the presence of renal adrenergic innervation. These data offer a fertile ground of therapeutic potential for the treatment of hypertension as well as open the door for further investigation into the mechanism involved in inflammation-mediated renal sodium transporter expression. Taken together, these findings suggest immune therapy, renal denervation, and, possibly, other new molecular targets as having a potential role in the development and maintenance of essential hypertension.

TRPC channels are not required for graded persistent activity in entorhinal cortex neurons.

Adaptive behavior requires the transient storage of information beyond the physical presence of external stimuli. This short-lasting form of memory involves sustained ("persistent") neuronal firing which may be generated by cell-autonomous biophysical properties of neurons or/and neural circuit dynamics. A number of studies from brain slices reports intrinsically generated persistent firing in cortical excitatory neurons following suprathreshold depolarization by intracellular current injection. In layer V (LV) neurons of the medial entorhinal cortex (mEC) persistent firing depends on the activation of cholinergic muscarinic receptors and is mediated by a calcium-activated nonselective cation current (ICAN ). The molecular identity of this conductance remains, however, unknown. Recently, it has been suggested that the underlying ion channels belong to the canonical transient receptor potential (TRPC) channel family and include heterotetramers of TRPC1/5, TRPC1/4, and/or TRPC1/4/5 channels. While this suggestion was based on pharmacological experiments and on effects of TRP-interacting peptides, an unambiguous proof based on TRPC channel-depleted animals is pending. Here, we used two different lines of TRPC channel knockout mice, either lacking TRPC1-, TRPC4-, and TRPC5-containing channels or lacking all seven members of the TRPC family. We report unchanged persistent activity in mEC LV neurons in these animals, ruling out that muscarinic-dependent persistent activity depends on TRPC channels.