心交感神経刺激時の神経伝達物質の動態と冠血管収縮

Quantitative Relationship between Neurotransmitters and Coronary Vascular Resistance during Cardiac Sympathetic Stimulation

　β受容体遮断の麻酔犬で，心交感神経刺激時の冠血管収縮に対する神経伝達物質の関与を定量的に解析した．星状神経節刺激時には，冠血管抵抗ならびにノルエピネフリンとニューロペプチド（NPY）オーバーフローが増大した．オーバーフローの程度はノルエピネフリンの方が約30倍大きく，冠血管抵抗と局所ノルエピネフリン濃度との間には有意な相関（r²＝0.333）がみられた．冠血管抵抗とNPY間には，β遮断下では有意な相関はみられなかったが，αβ両受容体遮断下では有意な相関（r²＝0.542）がみられた．冠動脈内投与による冠血管収縮作用は，重量濃度で換算するとノルエピネフリンとNPYとはほぼ同等であり，モル濃度ではNPYの作用が大であった．NPYの作用はα遮断薬で影響を受けなかった．結論：交感神経刺激時の内因性NPYの効果は同時に放出されるノルエピネフリンの効果によりマスクされている．

To investigate the effects of sympathetic neurotrans-mitters on coronary vasoconstriction, we examined the quantitative relationship of norepinephrine and neur-opeptide Y (NPY) levels to coronary vascular resis-tance (CVR) in 42 anesthetized dogs under fi-adrenoce-ptor blockade in a vagotomized condition. Endogenous norepinephrine levels correlated to CVR significantly (r²=0.333) during ansae subclaviae stimulation (2 and 20 Hz) but NPY did not, where norepinephrine-overflow was 30-fold larger than NPY-overflow. Under a-and )3-blockades, NPY levels significantly correlated to CVR (r²=0.542), whereas norepinephrine did not. Exogenous norepinephrine and NPY administered into the left circumflex artery (0.001 to 0.3μg/kg/min) had a similar coronary vasoconstrictive action in potency. Neither ATP, adenosine nor calcitonin gene-related peptide affected the sympathetic vasoconstriction dur-ing ventrolateral cardiac nerve stimulation (2 to 20 Hz). During the sympathetic nerve stimulation, there-fore, the vasocontrictive actions of NPY are concealed by norepinephrine under intact α-adrenoceptor condi-tions, manifest during α-blockade.