• The Korean Journal of Physiology
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• 제22권2호
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• pp.189-206
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• 1988

The effects of ouabain on the contractile and electrical activities were investigated in the isolated preparations of guinea-pig taenia coli, and compared with those of vanadate. Spontaneous contractions were recorded with force transducer, and electrical activites were measured by use of suction electrode, or single sucrose-gap technique. The contractions were induced by the electrical stimulation for 5 seconds every 1 minute with alternating current (60 Hz, 3.0 V/cm) through the platinum electrodes located in parallel with the long axis of the preparation. All experiments were performed in tris-buffered Tyrode solution which was aerated with $100%{\;}O_2$ and kept at $35^{\circ}C$. The results obtained were as follows: 1) Responses of spontaneous contractions to ouabain were concentration-dependent; $10^{-7}M$ ouabain caused a rise of basal tone. Above the concentration of $10^{-6}M$ ouabain, an initial increase followed by a decrease in tension was observed. 2) A continuous spike discharge was induced by the administration of $10^{-7}M$ ouabain. Above $10^{-6}M$ ouabain, a transient initial increase followed by a decrease in spike frequency and amplitude was produced, and finally membrane potential was sustained at a certain level without a spike discharge. 3) The characteristic response to $10^{-7}M$ ouabain was not blocked by the pretreatment with $10^{-7}M$ atropine. 4) The electrically induced contractions were completely suppressed at the concentration of $2{\times}10^{-7}M$ ouabain. These contractions were blocked more rapidly in paralled with the increase in ouabain concentration. 5) Effects of vanadate on the spontaneous activities were quite different from those of ouabain; $10^{-6}M$ vanadate increased the amplitude of contractions and $10^{-5}M$ vanadate increased slightly both amplitude and frequency of spontaneous contractions. $10^{-4}M$ vanadate showed irregular phasic contractions superimposed on the increased basal tone. 6) $10^{-5}M$ vanadate depolarized the membrane potential and shortened the interval between the bursts of spike discharge, whereas $10^{-4}M$ vanadate induced continuous spike discharge with membrane depolarization. 7) Vanadate caused a characteristic inhibitory response to the contractions induced by electrical stimulation; An initial rapid inhibition of tension development and then gradual recovery to a certain level. From the above results, the following conclusions could be made: 1) The rise of basal tone at $10^{-7}M$ ouabain is due to continuous spike discharge without a silent period. The continuous spike discharge is likely to be associated with a slight membrane depolarization caused by the blockage of Na pump. 2) The biphasic response induced by above $10^{-6}M$ ouabain seems to occur by the different mechanisms. The initial increase in tension is associated with depolarization along with an increase in spike frquency, whereas the subsequent relaxation occurs through a non-electrical mechanism. 3) The characteristic response to $10^{-7}M$ ouabain is resulted not from the action on intrinsic nerve terminal, but from its direct action on the membrane of smooth muscle cells. 4) The phasic contractions superimposed on the increased basal tone at the concentration of $10^{-4}M$ vanadate is resulted from the continuous spike discharge with membrane depolarization, of which mechanism remains unknown. 5) The inhibitory action of ouabain on the electrically induced contractions suggests that the increasein intracellular Na in some way inhibits the electrically induced $Ca^{2+}$ influx. The mechanism of vanadate action on the induced contractions remains unknown.

• The Korean Journal of Physiology
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• 제20권1호
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• pp.1-7
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• 1986

췌장의 분비기능에 대한 자율신경계의 영향은 이미 잘 알려져있다. 그러나 자율신경계를 거쳐 위장계의 기능을 조절하는 중추신경계가 췌장의 분비기능에 미치는 영향은 아직 알려져 있지 않다. 그러므로 본 연구에서는 자율신경계의 작용을 통합하는 기능을 지닌 것으로 여겨지는 중뇌의 망상체가 췌장의 분비기능에 미치는 영향을 알아보고자 하였다. 24시간 절식시킨 흰쥐 22마리를 urethane으로 마취하고 췌장액을 채취하기 위하여 췌장관에 가는 관을 삽입하였으며 담즙은 공장으로 우회시켰다. 또한 위액이 십이지장으로 넘어오지 못하도록 위-십이지장 연결부를 결찰하였다. 뇌정위 고정장치를 이용하여 중뇌의 망상체에 양측성으로 전극을 삽입하였다. 10분간에 흘러나오는 췌장액의 분비량이 일정하게 되었을때 전기자극 발생장치에서 얻어지는 1.3 V, 40Hz, 2msec의 전기자극을 이미 삽입한 전극을 통하여 망상체에 10분간 가하였다. 이어서 경부에서 미주신경을 양측성으로 절단하거나 또는 ${\beta}-adrenoceptor$의 길항체인 propranolol을 0.1mg/kg되게 경정맥을 통하여 주입하였으며, 10분이 경과한 다음에 망상체의 전기자극을 반복하였다. 이상의 실험이 끝나면 10% formalinedyddor을 심장을 통하여 관류하여 뇌를 고정하였으며 후에 전극의 위치를 조직학적으로 확인하였다. 채취한 췌장액으로부터 단백질 분비량과 amylase 분비량을 측정하였다. 중뇌의 망상체를 전기자극하면 췌장액의 분비량$({\mu}l/10min)$, 단백질분비량$({\mu}g/10min)$ 그리고 amylase분비량(U/10min) 모두가 유의하게 증가하였다. 이러한 망상체의 자극효과는 미주신경의 절단에 의하여서는 아무런 영향을 받지 않았으나 propranolol의 투여에 의하여서는 완전히 억제되었다. 또한 미주신경의 절단과 propranolol의 투여에 의하여 췌장의 분비기능이 유의하게 감소함을 관찰하겠다. 이상의 결과로 미루어보아 마취된 흰쥐에서 중뇌의 망상체는 췌장의 분비기능에 촉진적인 영향을 미치며, 이러한 영향은 교감신경계의 ${\beta}-receptor$를 거쳐 일어나는 것으로 생각된다.