Pharmacological properties were compared in the epididymal and prostatic portions of the rat vas deferens. 2. Contractile response to norepinephrine (NE) was larger in the epididymal portion, in spite of the smaller diameter in this region. In contrast, contraction evoked by ATP or alpha,beta-methylene ATP (alpha,beta-mATP) was larger in the prostatic portion. The sensitivities to NE but not to alpha,beta-mATP are different in these portions. 3. ATP or NE facilitated the contraction induced by the other agonist, suggesting that they cooperatively elicit smooth muscle contraction. This cooperation was observed in both portions. 4. Neither the contraction elicited by the addition of Ca2+ to smooth muscle depolarized with 63.7 mM extracellular K+ nor the relaxation by nifedipine of the depolarized smooth muscle precontracted with 1.8 mM extracellular Ca2+ was regionally different. However, Bay k 8644 elicited contraction only in the epididymal portion. A combination of 5 mMK+ with Bay k 8644 also caused oscillatory contraction in the prostatic portion. 5. A radioligand binding study was performed using the microsomal fraction prepared separately from these portions. Both the dissociation constant and the maximum binding for 3H-nimodipine were smaller in the epididymal fraction than in the prostatic fraction. 6. These results suggest that 1. the NE-elicited contraction is more pronounced in the epididymal portion, 2. the purinoceptor-mediated contractions along the vas deferens are less heterogeneous, and 3. although the sensitivity to Bay k 8644 is higher in the epididymal portion, Ca2+ channel-mediated responses are not regionally different when they are fully activated.
摘要
对大鼠输精管的附睾段和前列腺段的药理特性进行了比较。2. 尽管附睾段直径较小，但对去甲肾上腺素（NE）的收缩反应在该段更大。相比之下，由ATP或α,β-亚甲基ATP（α,β-mATP）引起的收缩在前列腺段更大。这两段对NE的敏感性不同，但对α,β-mATP的敏感性无差异。3. ATP或NE促进了另一种激动剂诱导的收缩，表明它们协同引发平滑肌收缩。这种协同作用在两段均有观察到。4. 向用63.7 mM细胞外钾去极化的平滑肌中添加Ca2+所引发的收缩，以及硝苯地平对用1.8 mM细胞外钙预收缩的去极化平滑肌的舒张作用，在区域上并无差异。然而，Bay k 8644仅在附睾段引发收缩。5 mM钾与Bay k 8644的组合在前列腺段也引起了振荡性收缩。5. 使用从这些段分别制备的微粒体部分进行了放射性配体结合研究。附睾部分中3H-尼莫地平的解离常数和最大结合量均小于前列腺部分。6. 这些结果表明：1. NE引发的收缩在附睾段更明显；2. 沿输精管的嘌呤受体介导的收缩异质性较小；3. 尽管附睾段对Bay k 8644的敏感性较高，但当Ca2+通道介导的反应被充分激活时，它们在区域上并无差异。
