Cobine C A, Fong M, Hamilton R, Keef K D
Department of Physiology and Cell Biology, University of Nevada, Reno, NV 89557, USA.
Neurogastroenterol Motil. 2007 Nov;19(11):937-45. doi: 10.1111/j.1365-2982.2007.00982.x. Epub 2007 Aug 28.
Excitatory motor innervation to the internal anal sphincter (IAS) of the monkey, the rabbit and mouse were compared. Contractile responses to electrical field stimulation of nerves (EFS, atropine 1 micromol L(-1) and N(omega)-nitro-L-arginine 100 micromol L(-1) present throughout) were examined in isolated strips of IAS. In the monkey IAS, EFS caused frequency dependent (1-30 Hz) contractions which were abolished by guanethidine (10 micromol L(-1)) or phentolamine (3 micromol L(-1)). The sympathetic neurotransmitter noradrenaline (NA) also caused concentration-dependent (10 nmol L(-1)-100 micromol L(-1)) contractions which were abolished by phentolamine revealing a small relaxation that was abolished by propranolol (3 micromol L(-1)). In contrast, EFS caused only relaxation of the mouse and rabbit IAS which was not affected by guanethidine. Furthermore, NA relaxed these muscles and relaxation was nearly abolished by combined addition of phentolamine and propranolol. In conclusion, the monkey IAS is functionally innervated by sympathetic nerves that contract the muscle via excitatory alpha-adrenergic receptors. In contrast, no significant motor function could be identified for sympathetic nerves in the rabbit or mouse IAS although adrenergic receptors linked to muscle inhibition are present. These data reveal species dependent differences in sympathetic motor innervation and suggest that some species are more appropriate than others as models for motor innervation to the human IAS.
比较了猴子、兔子和小鼠肛门内括约肌（IAS）的兴奋性运动神经支配。在分离的IAS条带上检测了对神经电场刺激（EFS，全程存在1 μmol L⁻¹阿托品和100 μmol L⁻¹ N⁻硝基-L-精氨酸）的收缩反应。在猴子的IAS中，EFS引起频率依赖性（1 - 30 Hz）收缩，这些收缩被胍乙啶（10 μmol L⁻¹）或酚妥拉明（3 μmol L⁻¹）消除。交感神经递质去甲肾上腺素（NA）也引起浓度依赖性（10 nmol L⁻¹ - 100 μmol L⁻¹）收缩，酚妥拉明可消除这些收缩，同时显示出一种小的松弛，该松弛被普萘洛尔（3 μmol L⁻¹）消除。相比之下，EFS仅引起小鼠和兔子IAS的松弛，且不受胍乙啶影响。此外，NA使这些肌肉松弛，酚妥拉明和普萘洛尔联合添加几乎可消除这种松弛。总之，猴子的IAS在功能上由交感神经支配，这些交感神经通过兴奋性α-肾上腺素能受体使肌肉收缩。相比之下，兔子或小鼠的IAS中交感神经未发现明显的运动功能，尽管存在与肌肉抑制相关的肾上腺素能受体。这些数据揭示了交感运动神经支配的物种依赖性差异，并表明某些物种比其他物种更适合作为人类IAS运动神经支配的模型。
