Maggi C A, Zagorodnyuk V, Giuliani S
Pharmacology Department, A. Menarini Pharmaceuticals, Florence, Italy.
Neuroscience. 1994 Dec;63(4):1137-52. doi: 10.1016/0306-4522(94)90579-7.
We studied the relative contribution of tachykinin NK1 and NK2 receptors in producing nonadrenergic noncholinergic excitation of the circular muscle of the guinea-pig proximal colon in response to electrical field stimulation. All experiments were performed in the presence of atropine, guanethidine, indomethacin, apamin and L-nitroarginine. In organ bath experiments, electrical stimulation produced a tetrodotoxin-sensitive frequency-dependent contraction. The NK1 receptor antagonists, FK 888 (1-10 microM) and GR 82,334 (0.3-3 microM) markedly reduced but did not abolish the nonadrenergic noncholinergic response. The NK2 receptor antagonist, GR 94,800 (0.3-3 microM) was partly effective at 3 microM. The combined administration of FK 888 (10 microM) and GR 94,800 (3 microM) or GR 82,334 and GR 94,800 abolished the nonadrenergic noncholinergic contraction. The response to a prolonged period of stimulation (3 Hz for 5 min) was evenly depressed by FK 888 or GR 82,334, while GR 94,800 was more effective in inhibiting the late (87% inhibition) than the peak response (25% inhibition). In the presence of nifedipine (1 microM) a marked inhibition of the nonadrenergic noncholinergic contraction was observed and a time lag was evident between stimulus application and onset of contraction, which showed slow onset and offset kinetics. The nifedipine-resistant nonadrenergic noncholinergic contraction was unaffected by FK 888 or GR 82,334 but was suppressed by GR 94,800. Submaximally effective (1-3 nM) concentrations of substance P and neurokinin A produced distinct patterns of contraction: the response to substance P was fast and declined rapidly toward baseline; the response to neurokinin A was slow and sustained. In the presence of nifedipine, the response to substance P was greatly depressed and became slower in onset; nifedipine did not affect the contraction to neurokinin A but slowed its time-course. In sucrose gap experiments, either a short (10 Hz for 1 s) or a prolonged period of electrical stimulation (3 Hz for 3 min) evoked membrane depolarization, action potentials and contraction: in response to the "prolonged" stimulation, distinct phasic and tonic component of contraction were observed. Nifedipine abolished action potentials and the phasic contraction produced by a short period of stimulation, reduced by about 50% the maximal contraction developed during the prolonged stimulation without affecting the amplitude of the tonic response. In the presence of nifedipine, GR 82,334 (3 microM) blocked the membrane depolarization but did not affect contraction; GR 94,800 (0.1 microM) did not affect depolarization but abolished contraction.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了速激肽NK1和NK2受体在豚鼠近端结肠环形肌产生非肾上腺素能非胆碱能兴奋以响应电场刺激过程中的相对贡献。所有实验均在阿托品、胍乙啶、吲哚美辛、蜂毒明肽和L - 硝基精氨酸存在的情况下进行。在器官浴实验中，电刺激产生了对河豚毒素敏感的频率依赖性收缩。NK1受体拮抗剂FK 888（1 - 10微摩尔）和GR 82,334（0.3 - 3微摩尔）显著降低但并未消除非肾上腺素能非胆碱能反应。NK2受体拮抗剂GR 94,800（0.3 - 3微摩尔）在3微摩尔时部分有效。联合给予FK 888（10微摩尔）和GR 94,800（3微摩尔）或GR 82,334和GR 94,800可消除非肾上腺素能非胆碱能收缩。FK 888或GR 82,334可均匀抑制对长时间刺激（3赫兹，持续5分钟）的反应，而GR 94,800在抑制后期反应（87%抑制）方面比峰值反应（25%抑制）更有效。在硝苯地平（1微摩尔）存在的情况下，观察到非肾上腺素能非胆碱能收缩受到显著抑制，刺激施加与收缩开始之间存在明显的时间延迟，显示出缓慢的起始和消退动力学。硝苯地平耐药的非肾上腺素能非胆碱能收缩不受FK 888或GR 82,334影响，但被GR 94,800抑制。亚最大有效浓度（1 - 3纳摩尔）的P物质和神经激肽A产生了不同的收缩模式：对P物质的反应迅速且迅速向基线下降；对神经激肽A的反应缓慢且持续。在硝苯地平存在的情况下，对P物质的反应大大降低且起始变得更慢；硝苯地平不影响对神经激肽A的收缩，但减缓了其时间进程。在蔗糖间隙实验中，短时间（10赫兹，持续1秒）或长时间电刺激（3赫兹，持续3分钟）均可诱发膜去极化、动作电位和收缩：响应“长时间”刺激时，观察到明显的相位性和紧张性收缩成分。硝苯地平消除了短时间刺激产生的动作电位和相位性收缩，使长时间刺激期间产生的最大收缩降低约50%，而不影响紧张性反应的幅度。在硝苯地平存在的情况下，GR 82,334（3微摩尔）阻断膜去极化但不影响收缩；GR 94,800（0.1微摩尔）不影响去极化但消除收缩。（摘要截断于400字）
