Sibley G N
J Physiol. 1984 Sep;354:431-43. doi: 10.1113/jphysiol.1984.sp015386.
Spontaneous activity in bladder muscle strips from man, pig and rabbit has been compared using an in vitro superfusion technique. Field stimulation was used to study nerve-mediated activity. Bladder muscle strips from all areas of the rabbit bladder displayed rhythmic spontaneous activity. Spontaneous activity was regularly present in strips from the trigone region in man and pig, but was present in only 18 and 19% respectively of strips from the dome of the bladder. Strength-duration curves in the presence of tetrodotoxin (10(-7) g/ml) were constructed. The 'chronaxie' of the muscle was found to be considerably shorter than that of other smooth muscles, ranging from 6.1 ms in the rabbit to 12.9 ms in man. Frequency-response curves were constructed using trains of stimuli. The responses were not antagonized by hexamethonium (10(-4) M), but were markedly inhibited by tetrodotoxin (10(-7) g/ml), indicating that the responses were mediated by excitation of post-ganglionic nerves. Physostigmine (10(-7)-5 X 10(-6) M) produced a dose-related increase in the contractile response to field stimulation in all three species. Atropine (10(-8)-10(-6) M) produced an inhibition of the contractile response, but the maximum degree of inhibition differed considerably between the species. In the rabbit, 58% of the control response was attained, whilst in the pig this was only 22%. Atropine completely abolished nerve-mediated contractions in human bladder muscle. Phentolmaine (10(-7)-2.5 X 10(-7) M) had no significant effect on the frequency-response curve in any of the three species, and did not depress the atropine-resistant component in rabbit and pig. It is concluded that nerve-mediated activity in human bladder muscle is exclusively cholinergic, in contrast to most other mammals studied in which there is a significant non-cholinergic component. The finding of a shorter chronaxie in bladder muscle than in other smooth muscles suggests important differences in its physiological properties that merit further investigation.
运用体外灌流技术比较了人、猪和兔膀胱肌条的自发活动。采用场刺激研究神经介导的活动。兔膀胱所有区域的肌条均表现出节律性自发活动。人及猪膀胱三角区肌条有规律地出现自发活动，但膀胱顶部肌条分别仅有18%和19%出现自发活动。构建了存在河豚毒素（10⁻⁷g/ml）时的强度-时间曲线。发现该肌肉的“时值”比其他平滑肌短得多，兔的时值为6.1毫秒，人的为12.9毫秒。使用刺激串构建频率-反应曲线。六甲铵（10⁻⁴M）不拮抗反应，但河豚毒素（10⁻⁷g/ml）显著抑制反应，表明反应由节后神经兴奋介导。毒扁豆碱（10⁻⁷ - 5×10⁻⁶M）使所有三种动物对场刺激的收缩反应呈剂量依赖性增加。阿托品（10⁻⁸ - 10⁻⁶M）抑制收缩反应，但不同动物的最大抑制程度差异很大。在兔中，达到对照反应的58%，而在猪中仅为22%。阿托品完全消除人膀胱肌的神经介导收缩。酚妥拉明（10⁻⁷ - 2.5×10⁻⁷M）对三种动物中的任何一种的频率-反应曲线均无显著影响，且不抑制兔和猪中对阿托品耐药的成分。结论是，与大多数其他被研究的哺乳动物不同，人膀胱肌的神经介导活动完全是胆碱能的，在这些哺乳动物中存在显著的非胆碱能成分。膀胱肌时值比其他平滑肌短的发现表明其生理特性存在重要差异，值得进一步研究。
