The influence of NG-nitro-L-Arginine (L-NNA) on non-adrenergic non-cholinergic (NANC) relaxations induced by electrical field stimulation was investigated in circular muscle strips of the guinea-pig gastric fundus. 2. In the presence of 10(-6) M atropine and 4 x 10(-6) M guanethidine, electrical field stimulation (40 V, 1 ms, 0.125-16 Hz) with 10 s trains at 5 min intervals induced short-lasting, frequency-dependent relaxations. Continuous stimulation, with cumulative increase of the stimulation frequency, induced sustained frequency-dependent relaxations. Both types of response were abolished by 3 x 10(-6) M tetrodotoxin. 3. L-NNA (10(-5) M and 10(-4) M) concentration-dependently reduced both types of NANC response. Pre-incubation with 2 x 10(-3) M L-arginine prevented the inhibitory action of 10(-5) M L-NNA and partially antagonized that of 10(-4) M L-NNA. D-arginine (2 x 10(-3) M) did not protect against the inhibitory effect of L-NNA. 4. L-NNA did not consistently influence the basal tone of the tissues. L-Arginine and D-arginine likewise did not influence basal tone; they also had no influence on the electrically-induced NANC relaxations. 5. NO (10(-6)-10(-4) M) induced short-lasting concentration-dependent relaxations, while vasoactive intestinal polypeptide (VIP, (10(-9)-10(-7) M) induced more sustained relaxations, that developed at a slower rate. The NO- and VIP-induced relaxations were not influenced by 10(-4) M L-NNA.6. These results suggest that NO is involved in NANC neurotransmission of the guinea-pig gastric fundus; its contribution to sustained NANC relaxation in the guinea-pig gastric fundus is much more important than in the rat.
摘要
在豚鼠胃底环形肌条中研究了NG-硝基-L-精氨酸（L-NNA）对电场刺激诱导的非肾上腺素能非胆碱能（NANC）舒张的影响。2. 在存在10^(-6) M阿托品和4×10^(-6) M胍乙啶的情况下，以5分钟间隔施加10秒的电场刺激（40 V，1 ms，0.125 - 16 Hz）诱导出持续时间短、频率依赖性的舒张。连续刺激并累积增加刺激频率，诱导出持续的频率依赖性舒张。两种类型的反应均被3×10^(-6) M河豚毒素消除。3. L-NNA（10^(-5) M和10^(-4) M）浓度依赖性地降低两种类型的NANC反应。用2×10^(-3) M L-精氨酸预孵育可预防10^(-5) M L-NNA的抑制作用，并部分拮抗10^(-4) M L-NNA的抑制作用。D-精氨酸（2×10^(-3) M）不能防止L-NNA的抑制作用。4. L-NNA对组织的基础张力没有一致的影响。L-精氨酸和D-精氨酸同样不影响基础张力；它们对电诱导的NANC舒张也没有影响。5. 一氧化氮（NO，10^(-6) - 10^(-4) M）诱导持续时间短的浓度依赖性舒张，而血管活性肠肽（VIP，10^(-9) - 10^(-7) M）诱导更持久的舒张，其发展速度较慢。NO和VIP诱导的舒张不受10^(-4) M L-NNA的影响。6. 这些结果表明，NO参与豚鼠胃底的NANC神经传递；其对豚鼠胃底持续NANC舒张的贡献比在大鼠中重要得多。
