• Molecules and Cells
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• 제25권4호
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• pp.504-509
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• 2008

Three G-protein-linked acetylcholine receptors (GARs) exist in the nematode C. elegans. GAR-3 is pharmacologically most similar to mammalian muscarinic acetylcholine receptors (mAChRs). We observed that carbachol stimulated ERK1/2 activation in Chinese hamster ovary (CHO) cells stably expressing GAR-3b, the predominant alternatively spliced isoform of GAR-3. This effect was substantially reduced by the phospholipase C (PLC) inhibitor U73122 and the protein kinase C (PKC) inhibitor GF109203X, implying that PLC and PKC are involved in this process. On the other hand, GAR-3b-mediated ERK1/2 activation was inhibited by treatment with forskolin, an adenylate cyclase (AC) activator. This inhibitory effect was blocked by H89, an inhibitor of cAMP-dependent protein kinase A (PKA). These results suggest that GAR-3b-mediated ERK1/2 activation is negatively regulated by cAMP through PKA. Together our data show that GAR-3b mediates ERK1/2 activation in CHO cells and that GAR-3b can couple to both stimulatory and inhibitory pathways to modulate ERK1/2.

• 대한약침학회지
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• 제23권1호
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• pp.1-7
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• 2020

Nicotine, primary component of tobaco produces craving and withdrawal effect both in humans and animals. Nicotine shows a close resemblance to other addictive drugs in molecular, neuroanatomical and pharmacological, particularly the drugs which enhances the cognitive functions. Nicotine mainly shows its action through specific nicotinic acetylcholine receptors located in brain. It stimulates presynaptic acetylcholine receptors thereby enhancing Ach release and metabolism. Dopaminergic system is also stimulated by it, thus increasing the concentration of dopamine in nuclear accumbens. This property of nicotine according to various researchers is responsible for reinforcing behavioral change and dependence of nicotine. Various researchers have also depicted that some non dopaminergic systems are also involved for rewarding effect of nicotinic withdrawal. Neurological systems such as GABAergic, serotonergic, noradrenergic, and brain stem cholinergic may also be involved to mediate the actions of nicotine. Further, the neurobiological pathway to nicotine dependence might perhaps be appropriate to the attachment of nicotine to nicotinic acetylcholine receptors, peruse by stimulation of dopaminergic system and activation of general pharmacological changes that might be responsible for nicotine addiction. It is also suggested that MAO A and B both are restrained by nicotine. This enzyme helps in degradation dopamine, which is mainly responsible for nicotinic actions and dependence. Various questions remain uninsurable to nicotine mechanism and require more research. Also, various genetic methods united with modern instrumental analysis might result for more authentic information for nicotine addiction.

• The Korean Journal of Physiology
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• 제24권2호
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• pp.353-362
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• 1990

Fluoride (F-), a known stimulator of G-protein, induced strong contraction in rabbit trachealis muscle. $AlCl_3\;(5{\sim}20\;{\mu}M)$, which is required for G-protein stimulation by $F^-$, potentiated the contractile response to $F^-$. $Ca^{2+}-removal$ and verapamil, a calcium channel blocker, inhibited the fluoroaluminate-induced contraction. Fluoroaluminate increased $^{45}Ca$ influx in the absence and presence of verapamil. In heparin-loaded muscle high $K^+-induced$ contraction was not affected, but acetylcholine and fluoroaluminate-induced contractions were inhibited. The fluoroaluminate-induced contraction was partially relaxed by isoproterenol, a stimulator of adenylate cyclase. Pertussis toxin partially inhibited fluoroaluminate-induced contraction and potentiated isoproterenol-induced relaxation in the presence of fluoroaluminate, but had no effect on acetylcholine-induced contraction and the isoproterenol-induced relaxation in the presence of acetylcholine. These results suggest that fluoroaluminate has the ability to stimulate at least two putative G-proteins in rabbit trachealis muscle; One causes $Ca^{2+}$ influx through the potential-operated $Ca^{2+}$ channel and the other induces intracellular $Ca^{2+}$ release by the increase of inositol-1, 4, 5-triphosphate.

• Biomolecules & Therapeutics
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• 제30권1호
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• pp.90-97
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• 2022

Recently, increasing evidence suggests that neuroinflammation may be a critical factor in the development of Parkinson's disease (PD) in addition to the ratio of acetylcholine/dopamine because dopaminergic neurons are particularly vulnerable to inflammatory attack. In this study, we investigated whether botulinum neurotoxin A (BoNT-A) was effective for the treatment of PD through its anti-neuroinflammatory effects and the modulation of acetylcholine and dopamine release. We found that BoNT-A ameliorated MPTP and 6-OHDA-induced PD progression, reduced acetylcholine release, levels of IL-1β, IL-6 and TNF-α as well as GFAP expression, but enhanced dopamine release and tyrosine hydroxylase expression. These results indicated that BoNT-A had beneficial effects on MPTP or 6-OHDA-induced PD-like behavior impairments via its anti-neuroinflammation properties, recovering dopamine, and reducing acetylcholine release.

• 동의생리병리학회지
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• 제17권1호
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• pp.50-56
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• 2003

This research was done to make the effective prescription and cope with various senile dementia. So Sprague-Dawley rats were injected with ibotenate to make a damage on learning and memory functions. At first acquisition test and retention rest were done in the Morris water maze. And to evaluate the effects of the sample drug(TBM) on choline acetyltranferase and acetylcholine esterase, immunoreactive measurement and enzymatic activity measuring were carried out. The ibotenic acid were injected to hippocampus CA1 and CA3 area. The results were as following. TBM improved the learning ability in the acquisition test and memory function in the retention test significantly. And TBM increased the level of ChAT which is synthesizing acetylcholine in CA3 area, and at the same time it increased the level of AChE which is resolving acetylcholine. These results show that T8M improved the cholinergic catabolism and anabolism, and the increment of metabolic activity of cholinergic system. In other words, it contributes to the recovery of damaged learning and memory function by ibotenic acid. So it can be concluded that TBM will be helpful to cholinergic brain damage induced by primary or senile reduction of acetylcholine secretive activity.

• The Korean Journal of Physiology and Pharmacology
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• 제9권1호
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• pp.37-43
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• 2005

Our previous report demonstrated that chick myoblasts are equipped with $Ca^{2+}$-permeable stretchactivated channels and $Ca^{2+}-activated$ potassium channels ($K_{Ca}$), and that hyperpolarization-induced by $K_{Ca}$ channels provides driving force for $Ca^{2+}$ influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for $Ca^{2+}$ influx. Under cell-attatched patch configuration, ACh increased the open probability of $K_{Ca}$ channels from 0.007 to 0.055 only when extracellular $Ca^{2+}$ was present. Nicotine, a nAChR agonist, increased the open probability of $K_{Ca}$ channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of $K_{Ca}$ channel is sensitive to intracellular $Ca^{2+}$ level, nAChR seems to be capable of inducing $Ca^{2+}$ influx. Using the $Ca^{2+}$ imaging analysis, we were able to provide direct evidence that ACh induced $Ca^{2+}$ influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from $-12.5{\pm}3$ to $-31.2{\pm}5$ mV by generating the outward current through $K_{Ca}$ channels. These results suggest that activation of nAChR increases $Ca^{2+}$ influx, which activates $K_{Ca}$ channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

• Applied Biological Chemistry
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• 제50권2호
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• pp.127-131
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• 2007

일련의 새로운 3-benzylidenemyosmine 유도체들의 구조 변화와 미국 바퀴벌래(Periplaneta. americana L.)의 nicotin acetylcholine 수용체 (nAChRs) 사이의 결합 친화력 상수에 관한 정량적인 구조와 활성과의 관계를 분자 홀로그램(H) QSAR 방법으로 검토하였다. 친화력 상수에 관하여 가장 양호한 HQSAR 모델은 분자조각 크기 5${\sim}$8 bin 조건에서 유도된 모델(IV-2)이었다. HQSAR 모델(VI-2)은 높은 예측성(q$^2$=0.507)과 상관성(r$^2_{nev.}$=0.944)에 근거하여 양호한 통계값들을 나타내었다. 그리고 HQSAR 기여도로부터 결합 친화력 상수는 분자내 anabaseine 고리에 의존적이었으며 결합 친화력성이 높은 화합물들이 최적화된 모델(VI-2)에 의하여 설계되었다.

• The Korean Journal of Physiology
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• 제29권1호
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• pp.29-37
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• 1995

Gastric smooth muscle of guinea pigs was used to investigate whether the inhibitory effect of calcium antagonists on tonic contraction was accompanied by inhibition of phospholipase C activity. Tonic contraction and $[^{3}H]$ inositol phosphate (IP) formation in response to acetylcholine were measured after pretreatment with verapamil, nifedipine, 8-(N,N-diethylamino)octyl 3,4,5-trimethoxy-benzoate (TMB-8) or EGTA. Verapamil $(10\;{\mu}M)$, TMB-8 $(10\;{\mu}M)$ or EGTA (2 mM) significantly inhibited acetylcholine $(1\;{\mu}M)$-stimulated tonic contraction but nifedipine (100 nM) did not. Acetylcholine dose-dependently increased the formation of $[^{3}H]IP$. This effect was not observed in the presence of 2 mM EGTA. Both verapamil and TMB-8 significantly inhibited $[^{3}H]IP$ formation induced by $10\;{\mu}M$ acetylcholine, whereas nifedipine did not. In a subsequent study, we measured phospholipase C activity in gastric muscle cell homogenate and in permeabilized cells to determine whether calcium antagonists could inhibit the activity directly. The calcium antagonists did not change the phospholipase C activity of the cell homogenate or the permeabilized cells. But EGTA decreased phospholipase C activity by 50%. These results suggest that the inhibitory effects of verapamil and TMB-8 on acetylcholine-stimulated tonic contraction may be accompanied by inhibition of phospholipase C activity.

• The Korean Journal of Physiology
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• 제14권2호
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• pp.21-28
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• 1980

In order to investigate the effect of cholinergic substance on the electrical and the mechanical activities of the stomach muscle, 10 isolated cat stomachs were studied. At various sites of a stomach muscle preparation, the electrical activity was monopolarly recorded by using capillary electrodes containing chlorided silver wires, and the isometric contractile activity was recorded simultaneously at the terminal portion of the antrum in Krebs solution$(36^{\circ}C)$ which was aerated with a gas mixture consisting of 95% $O_2$ and 5% $CO_2$. The recording of these activities were performed before (control period) and after acetylcholine$(10^{-5}M)$ and atropine $(10^{-6}M)$ administrations serially. Following results were obtained: 1) The mean frequency of the slow wave was $4.36{\pm}0.22\;cycles/min$ at all the various sites of the cat stomach. The slow wave was propagated caudad in sequence and its velosity of propagation increased as the slow wave approached the pylorus in normal Krebs solution. 2) After acetylcholine administration, the frequency of the slow wave increased transiently and the increase of slow wave frequency was followed by the isometric contraction of antral muscle in association with the second potential which succeeded the slow wave. 3) By atropine administration, the stimulatory effect of acetylcholine on the antral muscle contraction was abolished completely, and the frequency of the slow wave decreased significantly compared with that of the control period, which tendency was more prominent in the antrum. The above results suggest that the transient increase in the frequency of gastric slow wave by acetylcholine may have some influence upon the contraction mechanism of the cat antral muscle.

• 한국동물학회지
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• 제30권2호
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• pp.193-209
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• 1987

Patterns of amylase secretion in mouse pancreatic fragments were studied over a period of time after the tissue was stimulated by acetyicholine and MNNG. MNNG is known to activate guanylate cyclase and thus increase the cGMP concentration in the pancreatic acinar cell. These amylase secretion patterns were studied to investigate the role of cGMP in reaction cascade during secretion response of the tissues stimulated by acetyicholine. Cellular response of amylase secretion in the pancreas by acetyicholine was divided into two phases. During the first phase, zymogen granules which had existed in the cells were secreted by the action of $Ca^2$+ and calmodulin immediately after secretagogue administration, this being known as the initial response. When the tissue was stimulated by acetylcholine in a $Ca^2$+-deficient medium or one containing trifluoperazine as a calmodulin antagonist, this initial response was reduced. In the second phase, newly formed zymogen granules were secreted as sustained response after protein synthesis was triggered by secretagogue. This response was provoked by an activation of protein kinase C. When either cycloheximide as a protein synthesis inhibitor or dibucaine as a protein kinase C inhibitor were added to the incubation medium, this sustained response was remarkablely depressed in the pancreatic fragments stimulated with acetylcholine. In the pancreatic acinar cell, phosphatidylinositol turnover plays an important role in the secretion response and hexachlorocyclohexane inhibits this phosphatidylinositol turnover. The pancreatic tissue treated with the hexachlorocyclohexane exhibited inhibition on both initial and sustained responses of amylase secretion by acetylcholine. MNNG also accelerated amylase secretion from the tissue gradually along incubation time. The 22 minutes fraction of the pancratic secretion after administration of both acetylcholine and MNNG showed higher amylase activity than the neighboring fractions. Guanylate cyclase potentiated the sustained response. Even if it is experimented with an indirect method, guanylate cyclase was found responsible for activation of the sustained response of a step prior to the action of protein kinase C. As conclusion, it was considered that amylase secretion in mouse pancreatic fragments stimulated by acetylcholine is a three phasic response.