Horackova M, Huang M H, Armour J A
Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Cardiovasc Res. 1994 May;28(5):673-9. doi: 10.1093/cvr/28.5.673.
To determine the capacity of ATP to modify cardiomyocytes directly or indirectly via peripheral autonomic neurones, the effects of various purinergic agents were studied on long term cultures of adult guinea pig ventricular myocytes and their co-cultures with extracardiac (stellate ganglion) or intrinsic cardiac neurones.
Ventricular myocytes and cardiac neurones were enzymatically dissociated and plated together or alone (myocytes only). Myocyte cultures were used for experiments after three to six weeks. The electrical and contractile properties of cultured myocytes and myocyte-neuronal networks were investigated.
The spontaneous beating frequency of ventricular myocytes co-cultured with stellate ganglion neurones increased by approximately 140% (p < 0.001) following superfusion with 10(-5) M ATP. This effect was not modified significantly by tetrodotoxin or by beta adrenoceptor blockade (10(-5) M timolol), but was eliminated following application of the P2 antagonist suramin (10(-5) M). Basal spontaneous contractile rate was reduced by approximately 86% (p < 0.001) in the presence of suramin, indicating the existence of tonically active purinergic synaptic mechanisms in stellate ganglion neurone-myocyte cocultures. Suramin did not significantly affect non-innervated myocyte cultures. ATP increased myocyte contractile rate in intrinsic cardiac neurone-myocyte co-cultures by approximately 40% (p < 0.01) under control conditions, but when beta adrenergic receptors of tetrodotoxin sensitive neural responses were blocked, ATP induced greater augmentation (> 100%). In contrast, ATP induced much smaller effects in non-innervated myocyte cultures (approximately 26%, p < 0.01). Analogues of AT) showed the following order of potency: ATP > UTP > MSATP > beta gamma ATP > alpha beta ATP. Adenosine (10(-4) M) attenuated the beating frequency of myocytes in both types of co-culture, while not significantly affecting non-innervated myocyte cultures.
The experimental model used in this study showed that extrinsic and intrinsic cardiac neurones which possess P2 receptors can greatly enhance cardiac myocyte contractile rate when activated by ATP. Since adenosine reduced contractile rate in both types of co-cultures while not affecting non-innervated myocytes, it is concluded that some of these neurones possess P1 receptors.
为了确定三磷酸腺苷（ATP）直接或通过外周自主神经元间接修饰心肌细胞的能力，研究了各种嘌呤能药物对成年豚鼠心室肌细胞长期培养物及其与心外（星状神经节）或心脏固有神经元共培养物的影响。
心室肌细胞和心脏神经元通过酶解分离，然后一起或单独（仅肌细胞）接种培养。肌细胞培养物在三到六周后用于实验。研究了培养的肌细胞和肌细胞 - 神经元网络的电特性和收缩特性。
用10⁻⁵ M ATP灌注后，与星状神经节神经元共培养的心室肌细胞的自发搏动频率增加了约140%（p < 0.001）。河豚毒素或β肾上腺素能受体阻断剂（10⁻⁵ M噻吗洛尔）对这种效应没有显著影响，但应用P2拮抗剂苏拉明（10⁻⁵ M）后这种效应消失。在存在苏拉明的情况下，基础自发收缩率降低了约86%（p < 0.001），这表明在星状神经节神经元 - 肌细胞共培养物中存在持续活跃的嘌呤能突触机制。苏拉明对未受神经支配的肌细胞培养物没有显著影响。在对照条件下，ATP使心脏固有神经元 - 肌细胞共培养物中的肌细胞收缩率增加了约40%（p < 0.01），但当河豚毒素敏感的神经反应的β肾上腺素能受体被阻断时，ATP诱导的增强作用更大（> 100%）。相比之下，ATP在未受神经支配的肌细胞培养物中诱导的效应要小得多（约26%，p < 0.01）。ATP类似物的效力顺序如下：ATP > UTP > MSATP > βγATP > αβATP。腺苷（10⁻⁴ M）降低了两种共培养类型中肌细胞的搏动频率，而对未受神经支配的肌细胞培养物没有显著影响。
本研究中使用的实验模型表明，具有P2受体的心脏外在和固有神经元在被ATP激活时可大大提高心肌细胞的收缩率。由于腺苷降低了两种共培养类型中的收缩率，而不影响未受神经支配的肌细胞，因此得出结论，这些神经元中的一些具有P1受体。
