Hayashida H, Okamura T, Tomoyoshi T, Toda N
Department of Urology, Shiga University of Medical Sciences, Ohtsu, Japan.
J Urol. 1996 Mar;155(3):1122-7.
The aim of the present study is to analyze mechanisms underlying neurogenic relaxation of the corpus cavernosum which are believed to participate in penile erection.
Mechanical responses to nerve stimulation by electrical pulses and nicotine were measured in strips of canine corpus cavernosum precontracted with phenylephrine. Cyclic guanosine monophosphate (GMP) contents in the strips were also measured by radioimmunoassay. Immunohistochemistry for nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) was performed.
Transmural electrical stimulation and nicotine produced relaxations in the isolated canine corpus. The neurogenic relaxation was abolished by N omega-nitro-L-arginine, a NOS inhibitor, and the inhibition was reversed by L-arginine. Relaxations induced by nerve stimulation and exogenous nitric oxide (NO) were depressed by oxyhemoglobin and methylene blue. Vasoactive intestinal polypeptide (VIP)-induced relaxations were not influenced by these inhibitors. In the controls strips and those made unresponsive to VIP by its repeated application, the responses to nerve stimulation did not differ. The content of cyclic GMP in the tissue increased in response to nicotine, the effect being abolished by the NO synthase inhibitor. Immunohistochemical study demonstrated neurons containing NOS and VIP.
It appears that the relaxation induced by nerve stimulation is mediated solely by NO liberated from the nerve that activates soluble guanylate cyclase and increases the production of cyclic GMP in smooth muscle, whereas VIP does not play a role in the regulation of muscle tone under the experimental conditions used.
本研究旨在分析阴茎海绵体神经源性舒张的潜在机制，该机制被认为参与阴茎勃起过程。
在预先用去氧肾上腺素预收缩的犬阴茎海绵体条带上，测量电脉冲和尼古丁对神经刺激的机械反应。还用放射免疫分析法测量条带中环磷酸鸟苷（cGMP）的含量。进行一氧化氮合酶（NOS）和血管活性肠肽（VIP）的免疫组织化学检测。
跨壁电刺激和尼古丁可使离体犬阴茎海绵体产生舒张。NOS抑制剂Nω-硝基-L-精氨酸可消除神经源性舒张，L-精氨酸可逆转这种抑制作用。神经刺激和外源性一氧化氮（NO）诱导的舒张可被氧合血红蛋白和亚甲蓝抑制。血管活性肠肽（VIP）诱导的舒张不受这些抑制剂影响。在对照条带和因反复应用VIP而对其无反应的条带中，对神经刺激的反应没有差异。组织中的环磷酸鸟苷含量因尼古丁而增加，一氧化氮合酶抑制剂可消除该效应。免疫组织化学研究显示含有NOS和VIP的神经元。
似乎神经刺激诱导的舒张仅由神经释放的NO介导，NO激活可溶性鸟苷酸环化酶并增加平滑肌中环磷酸鸟苷的生成，而在所用实验条件下，VIP在肌张力调节中不起作用。
