Zosky Graeme R, O'Shea James E
Faculty of Health, School of Medicine, University of Tasmania, Private Bag 34, Hobart, TAS, 7000, Australia.
Faculty of Science, School of Animal Biology, The University of Western Australia, Crawley, WA, 6008, Australia.
J Comp Physiol B. 2017 Jan;187(1):203-211. doi: 10.1007/s00360-016-1021-1. Epub 2016 Jul 21.
Evidence for a functional ventricular parasympathetic innervation of the mammalian heart between and within taxa remains controversial. We have previously proposed that the presence of a functional parasympathetic innervation of the ventricle was indicative of heterothermy, and is essential for maintaining ventricular stability at low body temperature. However, it is possible that the presence of such an innervation is also representative of the primitive mammalian state. In this study, we aimed to determine whether a functional parasympathetic innervation of the ventricle, that is capable of actively reducing the force of contraction, is present across metatherian mammals. Using in vitro isolated cardiac preparations, we examined evidence for a functional ventricular parasympathetic innervation of the ventricle in two species of metatherian mammal, one heterotherm (Western pygmy possum; Cercatetus concinnus) and one homeotherm (Golden bandicoot; Isoodon auratus), from different families to complement existing data from a heterothermic dasyurid. Both C. concinnus and I. auratus had a potent biphasic response to transmural electrical stimulation in both atrial and ventricular preparations. Both the decrease and increase in the force of contraction in response to stimulation were almost entirely blocked by the cholinergic and adrenergic antagonists, atropine and propranolol, respectively. These observations provide clear evidence for a parasympathetic innervation of the ventricle that is capable of directly influencing the force of contraction across metatherian mammals with different thermoregulatory strategies. While this innervation may facilitate heterothermy, this suggests that the presence of such an innervation pattern is indicative of the primitive mammalian state.
哺乳动物类群之间以及类群内部，心脏存在功能性心室副交感神经支配的证据仍存在争议。我们之前曾提出，心室存在功能性副交感神经支配表明动物具有异温性，并且对于在低温时维持心室稳定性至关重要。然而，这种神经支配的存在也有可能代表了原始哺乳动物的状态。在本研究中，我们旨在确定在有袋类哺乳动物中是否存在能够主动降低收缩力的功能性心室副交感神经支配。我们使用体外分离的心脏标本，检测了来自不同科的两种有袋类哺乳动物（一种异温动物，西部侏儒袋貂；Cercatetus concinnus，以及一种恒温动物，金袋狸；Isoodon auratus）心室功能性副交感神经支配的证据，以补充来自异温性袋鼬科动物的现有数据。C. concinnus和I. auratus的心房和心室标本对跨壁电刺激均有强烈的双相反应。刺激引起的收缩力下降和增加几乎分别完全被胆碱能拮抗剂阿托品和肾上腺素能拮抗剂普萘洛尔阻断。这些观察结果为心室的副交感神经支配提供了明确证据，这种神经支配能够直接影响具有不同体温调节策略的有袋类哺乳动物的收缩力。虽然这种神经支配可能有助于异温性，但这表明这种神经支配模式的存在代表了原始哺乳动物的状态。
