The Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA.
Neuroscience. 2010 Jun 30;168(2):335-45. doi: 10.1016/j.neuroscience.2010.03.061. Epub 2010 Apr 14.
Norepinephrine (NE) and ATP are co-released by periarterial sympathetic nerves. In mesenteric arteries (MA) from deoxycorticosterone-acetate (DOCA)-salt hypertensive rats, ATP, but not norepinephrine, release is impaired suggesting that their release may be regulated differently. We tested the hypothesis that different calcium channels contribute to ATP and norepinephrine release from sympathetic nerves in vitro in MA from normotensive and DOCA-salt hypertensive rats and that oxidative stress disrupts prejunctional regulation of co-transmission. Excitatory junction potentials (EJPs) were used to measure ATP release. Norepinephrine release was measured amperometrically with carbon-fiber microelectrodes. CdCl2 (30 microM) inhibited norepinephrine release in sham and DOCA-salt arteries by 78% and 85%, respectively. The N-type calcium channel antagonist, omega-conotoxin GVIA (CTX, 0.1 microM) inhibited norepinephrine release by 50% and 67% in normotensive and DOCA-salt arteries, respectively while CTX blocked EJPs. The P/Q-type calcium channel antagonist omega-agatoxin IVA (ATX; 0.03 microM) reduced norepinephrine release in sham but not DOCA-salt arteries and increased EJPs in sham but not DOCA-salt arteries. ATX did not increase EJPs in sham arteries in the presence of the alpha(2)-adrenergic receptor antagonist, yohimbine (1 microM). alpha(2)-Autoreceptor-sensitive EJP facilitation is impaired in DOCA-salt hypertension but this response is restored in DOCA-salt rats treated chronically with the antioxidant, apocynin. Apocynin restored alpha(2)-autoreceptor regulation of norepinephrine release. We conclude that ATP released from periarterial sympathetic nerves is controlled directly by N-type calcium channels. Norepinephrine release is controlled by N and P/Q type calcium channels. Norepinephrine release controlled by P/Q channels acts at alpha(2)-adrenergic receptors to inhibit norepinephrine release suggesting that there may be multiple pools of norepinephrine in periarterial sympathetic nerves. Regulation of norepinephrine release by alpha(2)-autoreceptors and P/Q-type channels is impaired in DOCA-salt hypertension and alpha(2)-autoreceptor function is disrupted by oxidative stress.
去氧皮质酮-醋酸盐（DOCA）盐性高血压大鼠的肠系膜动脉（MA）中，交感神经同时释放去甲肾上腺素（NE）和三磷酸腺苷（ATP）。然而，与 NE 释放不同，ATP 释放受损，这表明它们的释放可能受到不同的调控。我们假设，在正常血压和 DOCA 盐性高血压大鼠的 MA 中，不同的钙通道可能导致交感神经释放 ATP 和 NE，并且氧化应激会破坏共传递的节前调节。我们使用兴奋性突触后电位（EJP）来测量 ATP 的释放，用碳纤维微电极测量 NE 的释放。CdCl2（30μM）分别抑制 sham 和 DOCA 盐性动脉中的 NE 释放 78%和 85%。N 型钙通道拮抗剂ω-芋螺毒素 GVIA（CTX，0.1μM）分别抑制正常血压和 DOCA 盐性动脉中 NE 释放 50%和 67%，同时阻断 EJP。P/Q 型钙通道拮抗剂ω-海芋螺毒素 IVA（ATX；0.03μM）减少 sham 动脉中的 NE 释放，但不影响 DOCA 盐性动脉；在 sham 动脉中增加 EJP，但不影响 DOCA 盐性动脉。在 sham 动脉中，在存在α2-肾上腺素能受体拮抗剂育亨宾（1μM）的情况下，ATX 不增加 EJP。在 DOCA 盐性高血压中，α2-自身受体敏感的 EJP 易化受损，但在长期用抗氧化剂 apocynin 治疗的 DOCA 盐性高血压大鼠中，这种反应得到恢复。Apocynin 恢复了 α2-自身受体对 NE 释放的调节。我们的结论是，periarterial 交感神经释放的 ATP 受到 N 型钙通道的直接调控。NE 的释放受 N 和 P/Q 型钙通道的调控。由 P/Q 型钙通道控制的 NE 释放作用于α2-肾上腺素能受体，抑制 NE 释放，提示 periarterial 交感神经中可能存在多个 NE 池。在 DOCA 盐性高血压中，α2-自身受体和 P/Q 型通道对 NE 释放的调节受损，并且氧化应激破坏了α2-自身受体的功能。
