| Characterization of the drug receptors responsible for intestinal contraction in Israeli carp |
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Hyo-in Yun1, Kyong-oh Han1, Seung-chun Park1, Joon-hyoung Cho2, Tae-kwang Oh3 |
1College of Veterinary Medicine, Chungnam National University
2Veterinary Research Institute
3Genetic Engineering Research Institute, KAIST |
| 이스라엘잉어 장관 수축에 관여하는 약물수용체에 관한 연구 |
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윤효인1, 한경호1, 박승춘1, 조준형2, 오태광3 |
1충남대학교 수의과대학
2가축위생연구소
3한국과학기술원 유전공학연구소 |
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| Abstract |
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In order to elucidate the characterization of receptors involved in inestinal motility of Israeli carp, spontaneously contracting Israeli carp intestinal preperations were prepared and mounted in the organ chambers for contraction traicings using a polygraph. Various contractile agonists were treated and their dose-response curves were constructed. $EC_{50}$ values$(pD_2)$ of each agonist on specific receptors, $pA_2$ values of competitive antagonists against some agonists, and $K_1$, values of noncompetitive antagonists against some agonists were analyzed for characterization of receptors related with the intestinal contraction. Results obtained through the experiments were summarized as follows: 1. Acetylcholine(ACh) exhibited biphasic dose-response curves: initial ACh-induced dose dependent contractions were observed in pM levels but followed by decreased response in in-between concentration levels. Dose dependent contractions reappeared in ${mu}M$ level. The peaks in pM and ${mu}M$ levels appeared in $10^{-13}M$ and $3{ imes}10^{-5}M$, respectvely. 2. Carbachol(CaCh) exhibited dose dependent contractions from $10^{-9}M$ to $10^{-5}M$, and its $pD_2$ values were higher than those of ACh($5.60{pm}0.11$). ACh and CaCh exhibited equiactive contractions. Nicotine had no effects on contractile responses of Israeli carp intestine. 3. ACh-induced responses were inhibited by atropine($K_1:7{ imes}10^{-8}M$), a muscarinic antagonist, in a non-competitive manner. But CaCh-induced responses were inhibited by both antimuscarinic atropine($pA_2:9.52{pm}0.14$) and selective $M_2$ antagonistic 4-DAMP($pA_2:8.16{pm}0.09$), in competitive manners. Nicotine receptor antagonistic decamethonium and hexamethonium had no effects on ACh-and CaCh-induced contractions. Therefore, the cholinergic receptor related to intestinal motility of Israeli carp was assumed as $M_2$ type. 4. In Israeli carp intestine, 5-HT (serotonin) exhibited dose dependent contractions in concentration range from $10^{-8}M$ to $10^{-5}M$. The maximal responses, however, were corresponded to about 50% of those of ACh or CaCh. 5-HT induced contractions were inhibited by $5-HT_2$ antagonistic ketanserin ($K_1: 7.8{ imes}10^{-4}M$) in a non-competitive manner, but not by both of anti $5-HT_1$, spiperone and anti $5-HT_3$, MDL-72222. Hence, $5-HT_2$ receptors are suggested to be existed in Isreli carp intestine. |
| Key Words:
Israeli carp, drug receptor, muscarinic, 5-HT, 4-DAMP, spiperone |
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