• The Korean Journal of Physiology and Pharmacology
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• v.2 no.1
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• pp.31-39
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• 1998

As it has been reported that the depolarization induced acetylcholine (ACh) release is modulated by activation of presynaptic $A_1$ adenosine heteroreceptor and various lines of evidence suggest the $A_2$ adenosine receptor is present in the hippocampus. The present study was undertaken to delineate the role of adenosine receptors on the hippocampal ACh release. Slices from the rat hippocampus were equilibrated with $[^3H]choline$ and then the release amount of the labelled product, $[^3H]ACh$, which was evoked by electrical stimulation (rectangular pulses, 3 Hz, 2 ms, 24 mA, $5\;V/cm^{-1}$, 2 min), was measured, and the influence of various adenosine receptor-related agents on the evoked tritium outflow was investigated. And also, the drug-receptor binding assay was performed in order to confirm the presence of $A_1$ and $A_2$ adenosine receptors in the rat hippocampus. N-ethylcarboxamidoadenosine (NECA), a potent adenosine receptor agonist with nearly equal affinity at $A_1$ and $A_2$ adenosine receptors, in concentrations ranging from $1{\sim}30\;{\mu}M$, decreased the electrically-evoked $[^3H]ACh$ release in a concentration-dependent manner without affecting the basal rate of release. And the effect of NECA was significantly inhibited by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 2 ${\mu}M$), a selective $A_1$ adenosine receptor antagonist, but was not influenced by 3,7-dimethyl-1-propargylxanthine (DMPX, 5 ${\mu}M$), a specific $A_2$ adenosine receptor antagonist. $N^6-cyclopentyladenosine$ (CPA), a selective $A_1$ adenosine receptor agonist, in doses ranging from 0.1 to 10 ${\mu}M$, reduced evoked $[^3H]ACh$ release in a dose-dependent manner without the change of the basal release. And the effect of CPA was significantly inhibited by 2 ${\mu}M$ DPCPX treatment. 2-P-(2-carboxyethyl)-phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS-21680C), a potent $A_2$ adenosine receptor agonist, in concentrations ranging from 0.1 to 10 ${\mu}M$, did not alter the evoked ACh release. In the drug-receptor binding assay, the binding of $[^3H]2-chloro-N^6-cyclopentyladenosine$ ($[^3H]$CCPA) to the $A_1$ adenosine receptor of rat hippocampal membranes was inhibited by CPA ($K_i$ = 1.22 nM), NECA ($K_i=10.17 nM$) and DPCPX ($K_i=161.86 nM$), but not by CGS-21680C ($K_i=2,380 nM$) and DMPX ($K_i=22,367 nM$). However, the specific binding of $[^3H]CGS-21680C$ to the $A_2$ adenosine receptor was not observed. These results suggest that the $A_1$ adenosine heteroreceptor play an important role in evoked ACh release, but the presence of $A_2$ adenosine receptor is not confirmed in this study.

• Korean Journal of Veterinary Research
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• v.24 no.1
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• pp.17-23
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• 1984

To validate the physiological properties of the histamine receptors of ileal smooth muscle in dog, the effects of adrenergic-, cholineric-, and H-receptor antagonists on the responses of ileal smooth muscle strips to histamine were investigated. The results were summarized as follows; 1. Histamine caused the contraction of ileal smooth muscle and the contractile responses were increased between the concentration of histamine $10^{-7}M$ and $10^{-5}M$ with dose-dependent manner in dog. 2. The shorter the treatment interval of histamine, the lower the contractile activity until the treatment interval extended to 40 minutes. 3. The contractile response induced by histamine was completely blocked by the pre treatment with a $H_1$-receptor blocker, chlorpheniramine and not by the pretreatment with a $H_2$-receptor blockers cimetidine. 4. The contractile response induced by histamine was not blocked by the pretreatment with a cholinergic receptor blocker, atropine. 5. The contractile response induced by histamine was not blocked by the pretreatment with an ${\alpha}$-adrenergic receptor blocker, phenoxybenzamine, or a ${\beta}$-adrenergic receptor blocker, propranolol. From these results, it was suggested that the contraction induced by histamine was elicited through $H_1$-receptor on the ileal smooth muscle in dog.

• YAKHAK HOEJI
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• v.32 no.2
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• pp.101-111
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• 1988

$[^3H]$ Quinuclidinyl benzilate(QNB) binding assays were performed in the dog ventricular sarcolemma fraction enriched approx. 32-fold in sarcolemma compared to the starting homogenate to elucidate the effect of antihistaminics on cardiac muscarinic receptor. Chlorpheniramine(CHP) inhibited specific binding of $[^3H]$QNB and delayed the equilibrium binding. The rate constants at $37^{\circ}C$ for formation and dissociation of the QNB receptor complex were $0.38{\times}10^9\;M^{-1}$ and $1.6{\times}10^{-2}\;min^{-1}$, respectively. The mean value for the dissociation constant from the pairs of the rate constants was 43. 2 pM and this value was similar to the value(44.8pM) determined from Scatchard analysis. CHP decreased association rate constant, indicating increase in $K_D$ value. Decrease in affinity without affecting the binding site concentration$(B_{max})$ for $[^3H]$QNB binding by CHP was also demonstrated by Scatchard analysis. $K_i$ values for $H_i$-blockers that inhibited specific $[^3H]$QNB binding were $0.02{\sim}4.8{\mu}M$. Cimetidine with $K_i$ value of $230{\mu}M$, however, was ineffective in displacing $[^3H]$QNB binding at concentration of $50{\mu}M$. The Hill coefficient for $H_1$-blockers were about one. The results indicate that $H_1$-antihistaminics inhibit $[^3H]$ QNB binding by interaction with myocardiac muscarinic cholinergic receptor and anticholinergic side effects of these drugs are mainly due to this receptor blocking mechanism.

• Biomolecules & Therapeutics
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• v.2 no.4
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• pp.361-368
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• 1994

The nature of the muscarinic receptors in bovine adrenal medulla was investigated in this study. [$^3$H]Quinuclidinyl benzilate(QNB) specifically bound to a single class of muscarinic receptor with a $K_{D}$ value of about 70 pM in bovine adrenal medullary, cardiac ventricular and ileal homogenates. Pirenzepine inhibition curves of [$^3$H]QNB binding to cardiac ventricular and ileal homogenates were steep, indicating the presence of a single class of binding site for pirenzepine with a Ki value of 990 nM and 508 nM, respectively. However, pirenzepine/[$^3$H]QNB competition binding curves in adrenal medulla suggested the presence of two binding sites (Hill coefficient=0.59) with a high( $M_1$) and a low( $M_2$) affinity. Respective Ki values for pirenfepine were 16 nM and 633 nM, with 44% of total sites having a high affinity( $M_1$). Gallamine, which is selective to cardiac $M_2$-receptor, inhibited [$^3$H]QNB binding to adrenal medullary, cardiac ventricular and ileal homogenates with Ki values of 12 $\mu$M, 6 $\mu$M and 13 $\mu$M, respectively. Thus, the binding affinities of pirenzepine and gallamine for $M_2$-receptor in adrenal medulla were similar to those in ileum, which contains the $M_3$-receptor. These results indicate that the $M_1$- and $M_3$- muscarinic receptor subtypes coexist in the bovine adrenal medulla.a.

• Biomolecules & Therapeutics
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• v.3 no.3
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• pp.192-198
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• 1995

The affinity of mequitazine, a non-sedating antihistamine, for muscarinic receptors was evaluated in the guinea-pig ventricle and ileum by in vitro binding techniques and functional studies. In binding studies, [$^3$H]quinuclidinyl benzilate (QNB) identified a single class of muscarinic receptors with similar apparent $K_{D}$ value of about 100 pM in two tissues. Mequitazine inhibited [$^3$H]QNB binding to muscarinic receptors competitively. Analysis of the mequitazine inhibition curve of [$^3$H]QNB binding to ventricular microsome and ileal homogenate indicated the presence of a single homogeneous binding site with Ki value of 25 nM and 18 nM, respectively. In functional studies, mequitazine caused parallel rightward shifts of concentration-response curves for carbachol and histamine in the isolated guinea-pig ileum. The slope values obtained from Schild plot analysis for the antagonistic action of mequitazine on muscarinic and histamine $H_1$-receptors were not significantly different from unity. The p $A_2$values of mequitazine for muscarinic and histamine $H_1$-receptors were about 7.6 ( $K_{M}$= 25.1 nM) and 8.88 ( $K_{H}$= 1.32 nM), respectively. These results indicate that the muscarinic receptor blocking action of mequitazine is 15 times less potent than the $H_1$receptor blocking action, but high concentration of this drug may cause the peripheral muscarinic receptor blocking effect.t.t.t.

• YAKHAK HOEJI
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• v.43 no.5
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• pp.642-651
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• 1999

Nonsedating antihistamines do net cause sedation in therapeutic doses because these drugs hardly cross the blood-brain barrier. Since most of the peripheral side dffects of conventional antihistamines are related to their muscarinic receptor blocking action, the present study was performed to investigate whether nonsedating antihistamines interact with the muscarinic receptors and discriminate the muscarinic receptor subtypes in the rat cerebral microsomal fraction which containes both $M_1,{\;}M_2,{\;}M_3{\;}and{\;}M_4$ receptors. Five nonsedating antihistamines at high concentrations inhibited [$^3H$]QNB binding to the muscarinic receptor in a dose-dependent manner. The inhibition curves of these drugs except loratadine which showed positive cooperativity (nH=1.55) were steep (nH=1), indicating interaction with a single homogenous population of the binding sites. Astemizole, clemizole and mequitazine increased the $K_D$ value for [$^3H$]QNB without affecting the binding site concentrations, and this increase in the $K_D$ value resulted from the ability of these drugs to slow [$^3H$]QNB-receptor association. The Ki values of astemizole, clemizole and mequitazine for the inhibition for the inhibition of [$^3H$]QNB binding to muscarinic receptor were 0.58, 5.99 and $0.007{\;}{\mu}M$, respectively. However, loratadine and terfenadine inhibited noncompetitively [$^3H$]QNB binding with the normalized $IC_50$ value of about $2{\;}{\mu}M$. These results demonstrate that; 1) astemizole, clemizole and mequitazine interact directly with the muscarinic receptor at high concentrations; 2) muscarinic receptor blocking potency of these drugs varies widely among drugs; 3) these drugs do not discriminate between muscarinic receptor subtypes.

• YAKHAK HOEJI
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• v.37 no.4
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• pp.397-407
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• 1993

The muscarinic antagonist l-[benzilic-4,4'-$^3H$]quinuclidinyl benzilate([$^3H$]QNB) bound to a single class of muscarinic receptor with high affinity in guinea pig ileal membranes. The $K_{D}$ and B$_{max}$ values for [$^3H$]QNB calculated from analysis of saturation isotherms were 54 pM and 156fmol/mg, respectively. H$_{1}$-blockers inhibited [$^3H$]QNB binding to ileal membranes with $K_{i}$ values ranged from 0.008 $\mu{M}$ to 1.6 $\mu{M}$. The pseudo-Hill coefficients of H$_{1}$-blockers for inhibition of [$^3H$]QNB binding to the ileal membranes were close to unit. The $K_{i}$ values for H$_{1}$-blockers were similar to the $K_{M}$ values calculated by Schild plot of functional data obtained from inhibition of the carbachol-induced contraction in guinea-pig ileum, suggesting that binding of H$_{1}$-blockers vs [$^3H$]QNB in ileal membranes represents an interaction with a receptor of physiological relevance. The $K_{H}$ values of H$_{1}$-blockers for H$_{1}$-receptor estimated from inhibition of the histamine-induced contraction were the range of 0.15 nM to 56.5 nM. The $K_{M}$/K$_{H}$ ratio of H$_{1}$-blockers varied over a wide range of 3 to 2300. Thus, the antihistaminic potencies of H$_{1}$-blockers do not correlate with their antimuscarinic potencies, which suggest that antihistamines have different antimuscarinic potencies in therapeutic blood levels causing similar antiallergic effect. Among 13 traditional antihistaminics examined in this study, drug having the highest and the lowest $K_{M}$/K$_{H}$ ratio is triprolidine and diphenidol, respectively. The present results demonstrate that the antimuscarinic property of antihistamines is not necessary for their antiallergic effect, and data on the affinity of antihistamines for muscarinic and H$_{1}$-receptors can be an important parameter in the selection and evaluation of these drugs.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1992.05a
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• pp.45-45
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• 1992

Calcium channel에 작용하는 dihydropyridine(DHP) 계열의 calcium channel 효능제와 길항제의 caicium channel에 대한 작용과 muscarinic receptor에 대한 작용과의 관계를 조사하기 위하여 [$^3$H]QNB와 [$^3$H]nitrendipine 결합실험을 시행하고 이를 지표로 하여 칼슘효능제와 길항제의 이들 receptors에 대한 결합성질을 검토하였다. 본 연구결과 칼슘 channel 효능제인 Bay K 8644는 칼슘길항제인 nicardipine 및 nimodipine과 같이 고농도에서 muscarinic receptor에 대한 [$^3$H]QNB결합을 경쟁적으로 억제하였으며 이들 약물의 muscarinic receptor에 대한 Ki치는 각각 16.7 $\mu$M, 3.5 $\mu$M, 및 15.5 $\mu$M이었다. 한편, 이들 약물은 다같이 칼슘 channel의 high affinity DHP결합부위에 대한 [$^3$H]nitrendipine 결합을 억제하였으나 이 부위에 대한 Bay K 8644, nicardipine, 및 nimodipine의 Ki치는 각각 4 nM, 0.1 nM, 및 0.2 nM로서 muscarinic receptor에 대한 Ki치 보다 4,000-75,000배 작았다. 뿐만 아니라 [$^3$H]QNB결합을 완전히 차단하는 고농도의 atropine(1 $\mu$M)에 의해서도 [$^3$H]nitrendipine결합이 전혀 영향을 받지 않았다. 따라서 DHP계 약물의 muscarinic receptor에 대한 작용은 칼슘channel에 대한 이들 약물의 작용을 연구하거나 임상적 치료 목적으로 사용할때는 나타나지 않을 것으로 생각된다.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.290-290
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• 1994

The binding characteristic of oxomemazine to muscarinic receptor in the cerebrum, heart, and ileum were compared to those of pirenzepine to investigate whether oxomemazine could classify the muscarinic receptor subtypes. 〔$^3$H〕Quinucl idinyl benzilate(QNB) identified a single class of muscarinic receptors with apparent K$\sub$D/ value of about 60 pM in three tissues. Analysis of the pirenzepine inhibition curve of 〔$^3$H〕QNB binding to cerebral microsome indicated the presence of two receptor subtypes with high (Ki=16 nM, M$_1$-receptor) and low (Ki=400 nM, M$_2$-receptor) affinity for pirenzepine. Oxomemazine also identified two receptor subtypes with high (Ki=84 nM, On-receptor) and low (Ki=1 4 ${\mu}$M, O$\sub$L/-receptor) affinity in rat cerebral microsome, The percentage population of the M$_1$-and M$_2$-receptors to the total receptors were 61 : 39, and those of the O$\^$H/- and O$\sub$L/-receptors 39 : 61, respectively, However, the Hill coefficients of these two drugs for the inhibition of 〔$^3$H〕QNB binding to the heart and ileum were close to unity which indicated that these drugs bound to a uniform population of receptors in these two tissues. The Ki values for the low affinity sites of pirenzepine and oxomemazine in the cerebrum were similar to those of these drugs in the heart ileum. Both pirenzepine and oxomemazine increased K$\sub$D/ value for 〔$^3$H〕QNB without affecting the binding sites concentration and Hill coefficient for the 〔$^3$H〕QNB binding. Oxomemazine had a 10-fold lower affinity at Ma-receptors than at M$_1$-receptors, and pirenzepine a 8-fold lower affinity at O$\sub$L/-receptors than OH-receptors. Analysis of the shal low competition curves of oxomemazine for the H$_1$ receptors and pirenzepine for the O$\sub$L/-receptors yielded that 69% of the M$_1$-receptors were of the O$\sub$H/-receptors and the remaining 31% of the O$\sub$L/-receptors, and that 29% of the O$\sub$L/-receptors were of the M$_1$-receptors and 71% of the M$_2$-receptors. However, M$_2$ for oxomemazine and O$\sub$H/ for pirenzepine were composed of a uniform population. These results suggest that oxomemazine could discriminatethe muscarnic receptor subtypes and may subclassify the M$_1$-receptors into two subtypes.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.739-743
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• 2006

Synthesis of cholic acid-based tripodal receptor (1) and its high chloride ion affinity in comparison with that of chenodeoxycholic acid (2) and lithocholic acid-based receptor (3) was achieved. Anion binding affinities of the receptors were evaluated $by\;^1H$ NMR and ITC titrations. Tripodal receptor 1 showed a selective affinity for $CI ^-$ over $Br ^-$, $I^-$, $H_2 PO _4\;^-$, and $CH _3 CO_2\;^-$. The selectivity of 1 for $CI ^-$ is about 3 times that of $Br ^-$, and 17 times that for $H_2 PO_4\;^-$.