• 대한약리학회지
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• 제27권2호
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• pp.89-97
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• 1991

가토 해마(hippocampus)에서 acetylcholine(ACh) 유리에 미치는 cAMP의 역할에 관한 지견을 얻고자하여 $[^3H]-choline$으로 평형시킨 해마 slice 및 시냅토솜(synaptosome)을 사용하여 $[^3H]-ACh$ 유리에 미치는 여러가지 약물들의 영향을 관찰하였다. Adenylate cyclase 활성화제인 forskolin$(0.1{\sim}30{\mu}M)$은 전기 및 고농도 $K^+$ 자극에 의한 $[^3H]-ACh$ 유리를 용량 의존적으로 증가시켰으며, dbcAMP 또한 ACh 유리를 강화시켰다. Muscarine성 흥분제인 oxotremorine$(0.1{\sim}30{\mu}M)$은 전기 및 $K^+$ 자극에 의한 $[^3H]-ACh$ 유리 효과를 용량 의존적으로 감소시켰으며, 이러한 효과는 forskolin 및 atropine에 의하여 차단됨을 관찰할 수 있었다. 한편 $K^+-channel$ 억제제인 glibenclamide$(1,\;10{\mu}M)$는 자체로는 $K^+$ 자극에 의한 $[^3H]-ACh$ 유리를 약간 억제시킴을 관찰할 수 있었으며, 대량의 forskolin$(10\;{\mu}M)$에 의한 $[^3H]-ACh$의 증가효과를 감약시킴을 알 수 있었다. 이상의 실험 결과로 가토 해마의 presynaptic muscarinic autoreceptor를 통한 ACh 유리의 조절에는 세포내 cAMP의 관여가 확실하다 하겠으나, 일부 $K^+-currents$의 관여를 배제할 수는 없을 것으로 사료된다.

• BMB Reports
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• 제29권6호
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• pp.525-529
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• 1996

Ligand binding properties of muscarinic acetylcholine receptors (mAChRs) in the nematode Caenorhabditis elegans (C. elegans) were characterized by using filtration binding assays. Scatchard analysis using $[^{3}H]N-methylscopolamine$ ($[^{3}H]NMS$) showed that the dissociation constant ($K_d$) and the maximum binding value ($B_{max}$) were $3.3{\pm}0.8{\times}10^{10}$ M and $9.0{\pm}1.1$ fmol/mg protein, respectively. Binding competition experiments indicated that the affinities of C. elegans mAChRs to atropine, scopolamine, and oxotremorine were similar to those of mammalian mAChRs. Pirenzepine binding experiments revealed that the binding pattern of mAChRs in C. elegans closely resembled that of mAChRs in rat brain, suggesting that the receptors consist primarily of Ml subtype. The affinity of mAChRs for oxotrernorine was significantly affected by guanylylimidodiphosphate (Gpp(NH)p), a non hydrolyzable GTP analog, suggesting that mAChRs in C. elegans might be coupled to G proteins. The data presented here indicate the possibility that C. elegans provides a living animal model to study the action mode of the muscarinic cholinergic system.

• The Korean Journal of Physiology and Pharmacology
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• 제1권5호
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• pp.485-493
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• 1997

We investigated the effect of ${\alpha}-adrenergic$ and cholinergic receptor agonists on $Ca^{2+}$ current in adult rat trigeminal ganglion neurons using whole-cell patch clamp methods. The application of acetylcholine, carbachol, and oxotremorine ($50\;{\mu}M\;each$) produced a rapid and reversible reduction of the $Ca^{2+}$ current by $17{\pm}6%,\;19{\pm}3%,\;and\;18{\pm}4%$, respectively. Atropine, a muscarinic antagonist, blocked carbachol- induced $Ca^{2+}$ current inhibition to $3{\pm}1%$. Norepinephrine ($50\;{\mu}M$) reduced $Ca^{2+}$ current by $18{\pm}2%$, while clonidine ($50\;{\mu}M$), an ${\alpha}2-adrenergic$ receptor agonist, inhibited $Ca^{2+}$ current by only $4{\pm}1%$. Yohimbine, an ${\alpha}2-adrenergic$ receptor antagonist, did not block the inhibitory effect of norepinephrine on $Ca^{2+}$ current, whereas prazosin, an ${\alpha}1-adrenergic$ receptor antagonist, attenuated the inhibitory effect of norepinephrine on $Ca^{2+}$ current to $6{\pm}1%$. This pharmacology contrasts with ${\alpha}2-adrenergic$ receptor modulation of $Ca^{2+}$ channels in rat sympathetic neurons, which is sensitive to clonidine and blocked by yohimbine. Our data suggest that the modulation of voltage dependent $Ca^{2+}$ channel by norepinephrine is mediated via an α1-adrenergic receptor. Pretreatment with pertussis toxin (250 ng/ml) for 16 h greatly reduced norepinephrine- and carbachol-induced $Ca^{2+}$ current inhibition from $17{\pm}3%\;and\;18{\pm}3%\;to\;2{\pm}1%\;and\;2{\pm}1%$, respectively. These results demonstrate that norepinephrine, through an ${\alpha}1-adrenergic$ receptor, and carbachol, through a muscarinic receptor, inhibit $Ca^{2+}$ currents in adult rat trigeminal ganglion neurons via pertussis toxin sensitive GTP-binding proteins.

• 약학회지
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• 제36권3호
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• pp.220-229
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• 1992

The muscarinic acetylcholine receptors of the dog unpregant uterus were characterized using $[^3H]quinuclidinyl$ benzilate(QNB) as a radioligand and the binding of muscarinic receptor agonists and antagonists in the uterus was compared to that in the urinary bladder which contains almost exclusively the M2 receptors in order to determine the receptor subtypes in the uterus. $[^3H]QNB$ binding to uterus and bladder was rapid, saturable and reversible. Scatchard analysis of the saturation data gave linear plots and the Hill coefficients were close to unit, which indicated that each preparation contained a single population of specific binding sites for $[^3H]QNB$. The KD values(120 pM) for QNB were almost identical in both organs, whereas the $B_{max}$ value of 256 fmol/mg protein in the uterus was significantly different from that of 563 fmol/mg protein in the bladder. Muscarinic agonists and antagonists inhibited in a competitive manner the $[^3H]QNB$ binding to the same extent in both organs. The competition binding studies using antagonists(atropine and pirenzepine) exhibited a single binding site and this site had a low affinity for pirenzepine with the Ki value of about 330 nM. However, high and low affinity binding sites were observed with carbachol, methacholine and oxotremorine. These binding studies with agonists and antagonists did not show any differences in drug affinities between uterus and bladder. These results indicate that the muscarinic receptors in the uterus are M2 receptors which have a low affinity for pirenzepine.

• The Korean Journal of Physiology and Pharmacology
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• 제2권2호
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• pp.147-154
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• 1998

It was attempted to clarify the participation of $K^+-channels$ in the post-receptor mechanisms of the muscarinic and $A_1-adenosine$ receptor- mediated control of acetylcholine (ACh) release in the present study. Slices from the rat hippocampus were equilibrated with $[^3H]$choline and the release of the labelled products was evoked by electrical stimulation (3 Hz, 5 V/cm, 2 ms, rectangular pulses), and the influence of various agents on the evoked tritium-outflow was investigated. Oxotremorine (Oxo, $0.1{\sim}10\;{\mu}M$), a muscarinic agonist, and $N^6-cyclopentyladenosine$ (CPA, $1{\sim}30\;{\mu}M$), a specific $A_1-adenosine$ agonist, decreased the ACh release in a dose-dependent manner, without affecting the basal rate of release. 4-aminopyridine (4AP), a specific A-type $K^+-channel$ blocker ($1{\sim}100\;{\mu}M$), increased the evoked ACh release in a dose-related fashion, and the basal rate of release is increased by 3 and $100\;{\mu}M$. Tetraethylammonium (TEA), a non-specific $K^+-channel$ blocker ($0.1{\sim}10\;{\mu}M$), increased the evoked ACh release in a dose-dependent manner without affecting the basal release. The effects of Oxo and CPA were not affected by $3\;{\mu}M$ 4AP co-treatment, but 10 mM TEA significantly inhibited the effects of Oxo and CPA. 4AP ($10\;{\mu}M$)- and TEA (10 mM)-induced increments of evoked ACh release were completely abolished in Ca^{2+}-free$ medium, but these were recoverd in low Ca^{2+}$ medium. And the effects of $K^+-channel$ blockers in low Ca^{2+}$ medium were inhibited by $Mg^{2+}$ (4 mM) and abolished by $0.3\;{\mu}M$ tetrodotoxin (TTX). These results suggest that the changes in TEA-sensitive potassium channel permeability and the consequent limitation of Ca^{2+}$ influx are partly involved in the presynaptic modulation of the evoked ACh-release by muscarinic and $A_1-adenosine$ receptors of the rat hippocampus.

• 대한약리학회지
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• 제23권2호
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• pp.77-85
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• 1987

혈압과 심박수의 중추조절에 대한 복외측 연수의 choline성 수용체의 역할을 규명하기 위하여 본 연구를 실시하였다. urethane으로 마취한 흰쥐에서 신경흥분성 아미노산인 L-glutamate(300 ng/site)를 복외측 연수에 미세주사하여 승압부위 (VLPA)와 감압부위 (VLDA)를 각각 기능적으로 확인하였다. VLPA와 VLDA에 각각 여러가지 choline성 약물들과 choline성 수용체의 길항제들을 양측으로 미세주사하여 다음과 같은 결과를 관찰하였다. 1. VLPA에 ca.bachol(300 ng/site)를 미세주사한 후 현저한 혈압상승 및 빈맥이 일어났으며, 이 반응은 hexamethonium ($4\;{\mu}g/site$)의 전처치에 의하여 차단되지 않았다. 2. VLPA에 physostigmine (200 ng/site)과 oxot.emo.me (300 ng/site)을 미세주사한 후 각각 현저한 혈압상승이 일어났다. 3. VLPA에 atropine($4\;{\mu}g/site$)을 미세주사한 후 현저한 혈압하강 및 서맥이 일어났다. 4. VLDA에 acetylcholine(500 ng/site)과 dimethylphenylpipe.azinium (500 ng/site)을 미세주사한 후 각각 현저한 혈압하강 및 서맥이 일어났다. 5. VLDA에 acetylcholine(500 ng/site)을 미세주사한 후 유발된 혈압하강 및 서맥반응은 hexamethonium($4\;{\mu}g/site$) 전처치에 의하여 차단되었다. 이상의 결과로 보아 흰쥐의 복외측 연수의 승압부위에서는 muscarine성 수용체를 통하여 혈압상승 및 빈맥반응이 일어나고 감압부위에서는 nicotine성 수용체를 통하여 혈압하강 및 서맥 반응이 일어나는 것으로 사료된다.