Ball D C, Hicks J W
Department of Biomedical Sciences, Creighton University, Omaha, NE, USA.
Comp Biochem Physiol A Physiol. 1996 Feb;113(2):135-41. doi: 10.1016/0300-9629(95)02044-6.
Muscle strips were dissected from the ventricle of the turtle, Trachemys (Pseudemys) scripta. Individual strips were placed in a muscle bath, set at a resting tension of three grams and electrically paced at 24 min(-1) for a control period of 1 hr. Cumulative dose-response curves were constructed using the adrenergic agonist, epinephrine (Epi) and the cholinergic agonist, metacholine (MCh). The administration of Epi to the muscle bath resulted in a dose-dependent increase in active tension development. The maximum tension developed was 40% above the control values and the concentration producing a half-maximal response (EC50) was 7.5 x 10(-7) M. The positive inotropic effect of Epi was diminished following the administration 1 x 10(-7) M propranolol. This reduced the maximum active tension by over 80% at the highest dose of Epi. In addition, the EC50 was increased to 8.9 x 10(-6) M. The administration of MCh resulted in a dose-dependent decrease in active tension development. The maximum decrease in active tension was 35% below the control values and the EC50 was 2.5 x 10(-6) M. The negative inotropic effect of MCh was diminished by the application of 1 x 10(-6) M atropine, with the EC50 increasing to 2.5 x 10(-4) M. These findings show that the isolated, in vitro turtle ventricle responds to adrenergic and cholinergic agonist. The results of this study support the hypothesis that the ventricular function, in reptiles, is controlled by both subdivisions of the autonomic nervous system.
从彩龟（滑龟属）的心室中分离出肌肉条。将单个肌肉条置于肌肉浴槽中，设定静息张力为3克，并在24次/分钟的频率下进行电刺激，持续1小时作为对照期。使用肾上腺素能激动剂肾上腺素（Epi）和胆碱能激动剂乙酰甲胆碱（MCh）构建累积剂量-反应曲线。向肌肉浴槽中加入Epi会导致主动张力发展呈剂量依赖性增加。最大张力比对照值高出40%，产生半数最大反应的浓度（EC50）为7.5×10⁻⁷ M。给予1×10⁻⁷ M普萘洛尔后，Epi的正性肌力作用减弱。在最高剂量的Epi作用下，这使最大主动张力降低了80%以上。此外，EC50增加到8.9×10⁻⁶ M。给予MCh会导致主动张力发展呈剂量依赖性降低。主动张力的最大降低幅度比对照值低35%，EC50为2.5×10⁻⁶ M。应用1×10⁻⁶ M阿托品可减弱MCh的负性肌力作用，EC50增加到2.5×10⁻⁴ M。这些发现表明，离体的体外龟心室对肾上腺素能和胆碱能激动剂有反应。本研究结果支持以下假设：爬行动物的心室功能受自主神经系统的两个分支控制。
