초록
가토흉부대동백근에서 MeB와 gentian violet는 용량-의존성 수축반응을 일으켰으나 evans blue와 eosine yellowish는 전혀 수축반응을 일으키지 못하였다. MeB는 돼지 장간막 동맥에서도 용량-의존성 수축반응을 일으켰다. 양표본에서 MeB $10^{-4}$ M의 단회투여는 수축반응에 이어 이완반응이 나타나는 양상성 반응을 일으켰으나, tyramine은 지속적인 수축반응을 일으켰다. Tyramine의 수축반응은 반복적이었으나 MeB의 그것은 일차 수축반응후 $3{\sim}5$시간후까지도 반복되지 않았다. Tyramine $10^{-4}$ M의 최대 수축반응 상태에서 MeB $10^{-4}$ M의 추가투여는 현저한 추가수축반응을 일으켰으나 반대로 MeB의 최대수축반응 상태에서 tyramine의 추가투여는 그이상의 수축반응을 일으키지 못하였다. Tyramine과 MeB 수축반응은 교감신경계 악물로 소실 또는 유의하게 억제되었다. Tyramine 수축반응은 MeB 수축보다 guanethidine과 6-hydroxydopamine에 더 예민한 반면, $Ca^{2+}-free$ PSS와 reserpine에 대하여는 MeB 수축반응이 tyramine 수축보다 더 예민하였고 prazosin하에서는 두 수축반응이 비슷하게 억제되었다. MeB 수축반응은 6-hydroxydopamine으로 유의하게 억제는 되었으나 소실되지 않았고, MeB 수축반응 관찰후에는 tyramine 뿐만아니라 6-hydroxydopamine의 수축반응도 소실되었다. 이상의 성적은 가토흉부대동맥과 돼지 장간막동맥에서 MeB 수축반응은 부분적으로 세포외 calcium 의존성이고 adrenaline성 신경발단으로부터의 norepinephrine유리에 기인하며, MeB의 norepinephrine유리 및 고갈작용이 tyramine 또는 6-hydroxydopamine의 작용보다 더 강력함을 시사하고 있다.
Methylene Blue (MeB) and gentian violet $(10^{-6}{\sim}10^{-4}\;M)$ produced contractions in isolated thoracic aortic preparations of rabbits in a dose-dependent fashion, while other dyes, evans blue and eosine yellowish, did not affect the basal tension in the same range of doses. Porcine mesenteric arterial rings also responded to MeB with dose-dependent contractions. Single dose of $10^{-4}$ M MeB produced a biphasic response: contraction followed by relaxation. The contraction developed slowly within $2{\sim}4$ min and peaked in about 20 minutes and then slowly relaxed to the basal level. Tyramine $(10^{-4}\;M)$ also induced contraction but it developed faster and was more persistent than that of MeB. While the tyramine-induced tension was reproducible, the MeB-induced one wat not reiterable until 3 to 5 hours after washing out the MeB. Adding $10^{-4}$ M MeB further potentiated the contraction induced by $10^{-4}$ M tyramine. However, the MeB contraction was not affected by further addition or tyramine. Both tyramine- and MeB-induced tensions were abolished or significantly inhibited by pretreatment with various drugs acting on the sympathetic nervous system. The tyramine-induced tension was more sensitive to guanethidine and 6-hydroxydopamine than the MeB-induced tension, while the latter was more sensitive to $Ca^{2+}-free$ PSS and reserpine. But they have similar sensitivity to prazosin. The MeB-induced tension was significantly inhibited but not abolished by 6-hydroxydopamine pretreatment. However, either tyramine or 6-hydroxydopamine could not affect the basal tension of the ring that MeB once had been tested. These results suggest that MeB-induced contractions of rabbit thoracic aorta and porcine mesenteric artery result from a release of endogenous norepinephrine from adrenergic nerve endings and are dependent in part on extracellular calcium, and that the potency of MeB to release or to deplete norepinephrine is greater than that of either tyramine or 6-hydroxydopamine.
(Department of Pharmacology, Chonnam University Medical School)
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