Acetylcholine (ACh) is an important neuromodulator in various cognitive functions. However, it is unclear how ACh influences neural circuit dynamics by altering cellular properties. Here, we investigated how ACh influences reverberatory activity in cultured neuronal networks. We found that ACh suppressed the occurrence of evoked reverberation at low to moderate doses, but to a much lesser extent at high doses. Moreover, high doses of ACh caused a longer duration of evoked reverberation, and a higher occurrence of spontaneous activity. With whole-cell recording from single neurons, we found that ACh inhibited excitatory postsynaptic currents (EPSCs) while elevating neuronal firing in a dose-dependent manner. Furthermore, all ACh-induced cellular and network changes were blocked by muscarinic, but not nicotinic receptor antagonists. With computational modeling, we found that simulated changes in EPSCs and the excitability of single cells mimicking the effects of ACh indeed modulated the evoked network reverberation similar to experimental observations. Thus, ACh modulates network dynamics in a biphasic fashion, probably by inhibiting excitatory synaptic transmission and facilitating neuronal excitability through muscarinic signaling pathways.
Cholinergic Agents/pharmacology* ; Acetylcholine/metabolism* ; Neurons/metabolism* ; Synaptic Transmission/physiology*

It was reported that α7 nicotinic acetylcholine receptor (α7-nAChR) knockout (α7 KO) mice showed few functional phenotypes. The purpose of this study was to investigate the effect of α7 KO on the electrophysiological characteristics of hippocampus in mice. The effect of α7 KO on hippocampal CA3-CA1 synaptic transmission in mice was evaluated by standard extracellular field potential recordings. The electrophysiological phenotype of γ-aminobutyrate A receptors (GABA-Rs) of single hippocampal neuron was detected by perforated patch-clamp recordings. The results showed that, the slope of field excitatory postsynaptic potential (fEPSP) and carbachol-induced theta oscillation were significantly decreased in the hippocampal CA1 neurons of α7 KO mice, compared with those of wild type mice. Under the treatment of GABA-R agonist muscimol, the I-V curves of both the hippocampal CA1 and CA3 neurons of α7 KO mice shifted towards depolarizing direction obviously, compared with those of wild type mice. These results suggest that the hippocampal CA3-CA1 synaptic transmission in α7 KO mice was significantly impaired and GABA-R maturation was significantly delayed, indicating that the deletion of α7-nAChR gene could significantly change the electrophysiological function of the hippocampus. The results may provide a new understanding of the role of α7-nAChR in hippocampal function and associated diseases.
Animals ; Hippocampus ; cytology ; Mice ; Mice, Knockout ; Neurons ; physiology ; Phenotype ; Synaptic Transmission ; alpha7 Nicotinic Acetylcholine Receptor ; physiology

The autonomic nervous system consists of the sympathetic nervous system and the parasympathetic nervous system. These two systems control the heart and work in a reciprocal fashion to modulate myocardial energy metabolism, heart rate as well as blood pressure. Multiple cardiac pathological conditions are accompanied by autonomic imbalance, characterized by sympathetic overactivation and parasympathetic inhibition. Studies have shown that overactive sympathetic nervous system leads to increased cardiac inflammatory reaction. Orchestrated inflammatory response serves to clear dead cardiac tissue and activate reparative process, whereas excessive inflammation may result in pathological cardiac remodeling. Since the discovery of the α7 nicotinic acetylcholine receptor (α7nAChR)-mediated cholinergic anti-inflammatory pathway (CAP), the protective effects of the parasympathetic nervous system in cardiac inflammation have attracted more attention recently. In this review, we summarized the role and underlying mechanisms of the sympathetic and parasympathetic nervous systems in cardiac inflammation, in order to provide new insight into cardiac inflammatory response in cardiovascular diseases.
Autonomic Nervous System ; physiology ; Heart ; physiopathology ; Humans ; Inflammation ; physiopathology ; Parasympathetic Nervous System ; physiology ; alpha7 Nicotinic Acetylcholine Receptor ; physiology

Contraction of smooth muscle cells is triggered by an increase in cytosolic Ca(2+) upon agonist stimulation. Ca(2+) influx across the plasma membrane constitutes a major component of the agonist-induced response in smooth muscle cells. Traditionally, voltage-operated Ca(2+) channel (VOCC) is considered as the channel mediating the Ca(2+) entry. However, this view has been challenged by recent discoveries, which demonstrated that other types of ion channels, such as store-operated and/or receptor-operated Ca(2+) channels (SOCC and/or ROCC), also participate in Ca(2+) response induced by agonists in smooth muscle cells. SOCC is defined as the channel activated in response to the depletion of the internal Ca(2+) stores, an event secondary to G protein coupled receptor or receptor tyrosine kinase stimulation. The Ca(2+) flow mediated by SOCC is termed as capacitative Ca(2+) entry (CCE). Previous study from other group has demonstrated that VOCC played a predominant role in ACh-induced contraction of distal colon smooth muscle in guinea pig. However, whether SOCC participates in the agonist-induced contractile response in this particular tissue is unknown. The present study was performed to investigate the role of CCE in ACh-induced mechanical activity of distal colon smooth muscle in rats. The contractile function of the smooth muscle was assessed by measuring isometric force of isolated rat distal colon rings. We showed that both high extracellular K(+) (40 mmol/L) and ACh (5 mumol/L) evoked striking contraction of the smooth muscle. The contractile responses were almost abolished by removal of extracellular Ca(2+) with ethylene glycol-bis(2-aminoethylether)-N,N,N',N' tetraacetic acid (EGTA), suggesting a critical contribution of extracellular source of Ca(2+) to the contraction. Verapamil (5 mumol/L), an L-type VOCC blocker, significantly attenuated, but didn't completely eliminate the high K(+)- and ACh-induced contraction (74% and 41% for high K(+) and ACh, respectively), indicating that additional channels might be involved in the contractile mechanism. Furthermore, ACh only induced transient contractions in the absence of extracellular Ca(2+). Readmission of Ca(2+) into the extracellular compartment resulted in a significant and sustained increase in the tension of the smooth muscle. This response was not affected by verapamil (5 mumol/L) and Cd(2+) (5 mumol/L), both of which efficiently block VOCC at the doses. However, La(3+), a known inhibitor of SOCC, significantly suppressed the Ca(2+) readdition-induced contraction in a dose-dependent manner. On the basis of these results, we conclude that contraction of smooth muscle in the distal colon is regulated by multiple Ca(2+) channels. In addition to VOCC-mediated Ca(2+) influx, SOCC-mediated CCE participates in agonist-induced contractile response of distal colon smooth muscle in rats.
Acetylcholine ; physiology ; Animals ; Calcium ; metabolism ; Calcium Channels ; physiology ; Colon ; physiology ; Female ; Male ; Muscle Contraction ; physiology ; Muscle, Smooth ; physiology ; Myocytes, Smooth Muscle ; physiology ; Rats ; Rats, Sprague-Dawley ; Verapamil ; pharmacology

Molecular biological studies and electrophysiological data have demonstrated that acetylcholine (ACh) is the principal cochlear and vestibular efferent neurotransmitter among mammalians. However, the functional roles of ACh in type II vestibular hair cells among mammalians are still unclear, with the exception of the well-known alpha9-containing nicotinic ACh receptor (alpha9-nAChR) in cochlear hair cells and frog saccular hair cells. In this study, the properties of the ACh-sensitive current were investigated by whole-cell patch clamp technique in isolated type II vestibular hair cells of guinea pigs. The direct effect of extracellular ACh was to induce a hyperpolarization effect in type II vestibular hair cells. Type II vestibular hair cells displayed a sustained outward current in response to the perfusion of ACh. It took about 60 s for the ACh-sensitive current to get a complete re-activation. The reversal potential of the ACh-sensitive current was (-66 +/- 8) mV, which indicated that potassium ion was the main carrier of this current. The blocking effect by the submillimolar concentration of tetraethylammonium (TEA) further indicated that extracellular ACh stimulated the calcium-dependent potassium current. Following replacement of the compartment of NaCl in the normal external solution with TrisCl, LiCl or saccharose respectively, the amplitude of the ACh-sensitive current was not affected. Blocking of the release of intracellular Ca(2+) stores by intracellular application of heparin failed to inhibit the ACh-sensitive current. Therefore, extracellular Na(+)and the inositol 1,4,5-trisphosphate (IP(3))-dependent intracellular Ca(2+)release were not involved in the activation of the ACh-sensitive current. However, the ACh-sensitive current was strongly affected by the concentration of the extracellular K(+), extracellular Ca(2+) and intracellular Mg(2+). The amplitude of the ACh- sensitive current was strongly inhibited by high concentration of extracellular K(+). In the Ca(2+)-free external solution, ACh only activated a very small current; however, the ACh-sensitive current demonstrated a Ca(2+)-dependent inhibition effect in high concentration of Ca(2+)solution. In addition, the ACh-sensitive current was inhibited by increasing of the concentration of intracellular Mg(2+). In conclusion, the present results demonstrate that ACh plays an important role in the vestibular efferent system. The fact that Na(+) is not involved in the ACh-sensitive current will not favor the well-known profile of alpha9-nAChR, which is reported to display a small but important permeability to Na(+). It is also suggested that, in vivo, the amplitude of the ACh-induced hyperpolarization may strongly depend on the concentration of extracellular Ca(2+)and intracellular Mg(2+).
Acetylcholine ; physiology ; Animals ; Calcium ; physiology ; Guinea Pigs ; Hair Cells, Vestibular ; physiology ; Magnesium ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology

Experiments were designed to characterize the cellular mechanisms of action of endothelium-derived vasodilator substances in the rabbit femoral artery. Acetylcholine (ACh, 10(-8)-10(-5) M) induced a concentration-dependent relaxation of isolated endothelium-intact arterial rings precontracted with norepinephrine (NE, 10(-6) M). The ACh-induced response was abolished by the removal of endothelium. NG-nitro-L-arginine (L-NAME, 10(-4) M), an inhibitor of NO synthase, partially inhibited ACh-induced endothelium-dependent relaxation, whereas indomethacin (10(-5) M) showed no effect on ACh-induced relaxation. 25 mM KCl partially inhibited ACh-induced relaxation by shifting the concentration-response curve and abolished the response when combined with L-NAME and NE. In the presence of L-NAME, ACh-induced relaxation was unaffected by glibenclamide (10(-5) M) but significantly reduced by apamin (10(-6) M), and almost completely blocked by tetraethylammonium (TEA, 10(-3) M), iberiotoxin (10(-7) M) and 4-aminopyridine (4-AP, 5 x 10(-3) M). The cytochrome P450 inhibitors, 7-ethoxyresorufin (7-ER, 10(-5) M) and miconazole (10(-5) M) also significantly inhibited ACh-induced relaxation. Ouabain (10(-6) M), an inhibitor of Na+, K(+)-ATPase, or K(+)-free solution, also significantly inhibited ACh-induced relaxation. ACh-induced relaxation was not significantly inhibited by 18-alpha-glycyrrhetinic acid (18 alpha-GA, 10(-4) M). These results of this study indicate that ACh-induced endothelium-dependent relaxation of the rabbit femoral artery occurs via a mechanism that involves activation of Na+, K(+)-ATPase and/or activation of both the voltage-gated K+ channel (Kv) and the large-conductance, Ca(2+)-activated K+ channel (BKCa). The results further suggest that EDHF released by ACh may be a cytochrome P450 product.
Acetylcholine/pharmacology ; Animal ; Biological Factors/physiology* ; Female ; Femoral Artery/physiology* ; Femoral Artery/drug effects ; In Vitro ; Male ; Potassium Channels/physiology* ; Rabbits ; Vasodilation/physiology ; Vasodilator Agents/pharmacology

AIMTo explore the resistant arterial effect of superoxide anion and its possible mechanisms.

METHODSThe third branch of the superior mesenteric artery in male Sprague-Dawley (200-300 g) rats was rapidly excised. Periadventitial fats and connective tissues were removed and the artery was dissected into about 2 mm rings. Each ring was dispensed between two stainless steel wires (diameter 0.0394 mm) in a 5 ml organ bath (DMT 610 M, Danish Myo Technology, Denmark). Isometric force recording studies in vitro of rat mesenteric arterial rings were recorded by Powerlab Syetem. Exposure of arteries to superoxide was accomplished through the auto-oxidation of pyrogallol added to the artery baths. Then endothelium-dependent or independent relaxation was investigated, respectively.

RESULTSExposure to pyrogallol (10, 100, 300, and 1 000 micromol/L) which could produce superoxide anion for 15 min resulted in a dose-dependent manner in a decrease of acetylcholine(ACh)-induced relaxation in rat mesenteric artery. Especially, the two predominant components of acetylcholine(ACh)-induced endothelium-dependent relaxation, EDHF component and NO component were both inhibited by superoxide anion from pyrogallol. However, exposure to superoxide anion from pyrogallol had no effect on the endothelium-independent relaxations to pinacidil or sodium nitroprusside (SNP) in rat mesenteric artery.

CONCLUSIONThese results indicate that superoxide anion can inhibit the endothelium-dependent relaxation in rat mesenteric artery, but has no effect on the endothelium-independent relaxation, in which the inhibited effect of EDHF and NO from endothelium is involved.

Acetylcholine ; pharmacology ; Animals ; Endothelium-Dependent Relaxing Factors ; physiology ; In Vitro Techniques ; Male ; Mesenteric Arteries ; physiology ; Nitric Oxide ; physiology ; Rats ; Rats, Sprague-Dawley ; Superoxides ; pharmacology ; Vasodilation ; physiology

The aim of the present study is to explore the interaction of nitric oxide (NO) and nicotinic acetylcholine receptor (nAChR) on learning and memory of rats. Rats were intracerebroventricularly (i.c.v.) injected with L-arginine (L-Arg, the NO precursor) (L-Arg group) or choline chloride (CC, an agonist of α7nAChR) (CC group), and with combined injection of L-Arg and CC (L-Arg+CC group), and methyllycaconitine (MLA, α7nAChR antagonist) or N(ω)-nitro-L-arginine methylester (L-NAME, nitric oxide synthase inhibitor) i.c.v. injected first and followed by administration of L-Arg combined with CC (MLA+L-Arg+CC group or L-NAME+L-Arg+CC group), respectively, and normal saline was used as control (NS group). The learning and memory ability of rats was tested with Y-maze; the level of NO and the expressions of neuronal nitric oxide synthase (nNOS) or α7nAChR in hippocampus were measured by NO assay kit, immunohistochemistry or Western blot. The results showed that compared with L-Arg group or CC group, the rats' learning and memory behavioral ability in Y-maze was observably enhanced and the level of NO, the optical density of nNOS-like immunoreactivity (LI) or α7nAChR-LI in hippocampus were significantly increased in L-Arg+CC group; Compared with L-Arg+CC group, the ability of learning and memory and the level of NO as well as the expressions of nNOS-LI or α7nAChR-LI were obviously decreased in MLA+L-Arg+CC group or in L-NAME+L-Arg+CC group. In conclusion, i.c.v. administration of L-Arg combined with CC significantly improved the action of the L-Arg or CC on the content of NO and the nNOS or α7nAChR expressions in hippocampus along with the learning and memory behavior of rats; when nNOS or α7nAChR was interrupted in advance, the effects of L-Arg combined with CC were also suppressed. The results suggest that there are probably synergistic effects between NO and nAChR on learning and memory.
Animals ; Enzyme Inhibitors ; pharmacology ; Hippocampus ; physiology ; Learning ; Memory ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; physiology ; Nitric Oxide Synthase Type I ; physiology ; Rats ; alpha7 Nicotinic Acetylcholine Receptor ; physiology

The cholinergic anti-inflammatory pathway (CAP) is a neurophysiological mechanism that regulates the immune system. The CAP inhibits inflammation by suppressing cytokine synthesis via release of acetylcholine in organs of the reticuloendothelial system, including the lungs, spleen, liver, kidneys and gastrointestinal tract. Acetylcholine can interact with alpha7 nicotinic acetylcholine receptors (alpha7 nAchR) expressed by macrophages and other cytokine producing cells, down-regulate pro-inflammatory cytokine synthesis and prevent tissue damage. Herein is a review of the neurophysiological mechanism in which the CAP regulates inflammatory response, as well as its potential interventional strategy for inflammatory diseases.
Acetylcholine ; pharmacology ; Animals ; Humans ; Inflammation ; immunology ; prevention & control ; Myocardial Infarction ; immunology ; Pancreatitis ; immunology ; Receptors, Muscarinic ; physiology ; Receptors, Nicotinic ; physiology ; Reperfusion Injury ; immunology ; Sepsis ; immunology ; Shock, Hemorrhagic ; immunology ; Spleen ; immunology ; innervation ; Vagus Nerve ; physiology ; alpha7 Nicotinic Acetylcholine Receptor

OBJECTIVETo investigate the distribution and mechanism of coronary arteriole (CA) cell resting membrane potential (RP) in guinea pigs.

METHODSCell RP was recorded by intracellular microelectrode in isolated guinea pig coronary arteriole (diameter < 100 microm).

RESULTS(1) Experiments were carried out in 112 cells with a mean RP of (-65 +/- 4.2)mV, the distribution of coronary arteriole cell RP fitted by Gaussian function was bimodal, one peak was -43 mV termed high RP, the other was -74 mV termed low RP. 10 mmol/L K+ and 3 micromol/ L acetylcholine(ACh) induced hyperpolarization in high-RP cells with (-7.4 +/- 0.87) mV (n = 13) and (-15 +/- 1.24) mV (n = 16) respectively, and induced depolarization in low-RP cells with (9.6 +/- 1.2) mV (n = 23) and (8.7 +/- 0.69) mV (n = 15) respectively. (2) The inward rectifier K+ channel (K(ir)) blocker Ba2+ caused concentration-dependent depolarization in low-RP cells with an EC50 of 120 micromol/L 100 micromol/L Ba2+ or higher could shift low-RP cells to high-RP state, the response of these cells to high K+ and ACh became a hyperpolarization.

CONCLUSIONThe distribution of coronary vascular cell RP is bimodal, high K+ and ACh induce different responses in low and high RP cells. The two RP states are exchangeable mainly due to all-or-none conductance changes of K(ir).

Acetylcholine ; metabolism ; Animals ; Arterioles ; cytology ; Coronary Vessels ; cytology ; physiology ; Female ; Guinea Pigs ; Male ; Membrane Potentials ; physiology ; Microelectrodes ; Myocardium ; metabolism ; Potassium Channels, Inwardly Rectifying ; physiology