Williams J T, North R A
Neuroscience. 1985 Jan;14(1):103-9. doi: 10.1016/0306-4522(85)90167-8.
Intracellular recordings were made from neurones in the nucleus locus coeruleus in a slice of tissue cut from the rat pons. Clonidine (100 nM-10 microM), noradrenaline (10 microM-1 mM) and adrenaline (10 microM-1 mM) all reduced the duration of the spontaneously occurring action potential of the neurones. This effect was also observed on the action potential in the presence of tetrodotoxin, which results from calcium entering the cell. These concentrations of clonidine, noradrenaline and adrenaline always hyperpolarized the membrane. This hyperpolarization was prevented by two procedures which block potassium currents--intracellular caesium and extracellular barium. In conditions of potassium current blockade, noradrenaline (100 microM-1 mM) and adrenaline (20 microM-1 mM) shortened the calcium action potential but clonidine was ineffective even at 10 microM. Adrenaline and noradrenaline also suppressed inward calcium and barium currents measured under voltage clamp. This action of noradrenaline and adrenaline was not prevented by yohimbine (10 microM), propranolol (20 microM) or prazosin (1 microM); it was reduced by a concentration of phentolamine about 100 times higher than its Ke for alpha 2-adrenoceptors on locus coeruleus neurones. It is concluded that noradrenaline and adrenaline can directly inhibit calcium action potentials in locus coeruleus neurones when applied in high concentrations, but that this does not involve an alpha 2-adrenoceptor.
在从大鼠脑桥切下的组织切片中，对蓝斑核中的神经元进行了细胞内记录。可乐定（100 nM - 10 μM）、去甲肾上腺素（10 μM - 1 mM）和肾上腺素（10 μM - 1 mM）均缩短了神经元自发动作电位的持续时间。在存在河豚毒素的情况下，对动作电位也观察到了这种效应，这是由钙进入细胞引起的。这些浓度的可乐定、去甲肾上腺素和肾上腺素总是使膜超极化。这种超极化可通过两种阻断钾电流的方法来防止——细胞内铯和细胞外钡。在钾电流阻断的条件下，去甲肾上腺素（100 μM - 1 mM）和肾上腺素（20 μM - 1 mM）缩短了钙动作电位，但可乐定即使在10 μM时也无效。肾上腺素和去甲肾上腺素还抑制了在电压钳制下测量的内向钙电流和钡电流。去甲肾上腺素和肾上腺素的这种作用不受育亨宾（10 μM）、普萘洛尔（20 μM）或哌唑嗪（1 μM）的影响；它被一种酚妥拉明浓度降低，该浓度比其对蓝斑核神经元α2 - 肾上腺素能受体的解离常数高约100倍。结论是，高浓度应用时，去甲肾上腺素和肾上腺素可直接抑制蓝斑核神经元中的钙动作电位，但这并不涉及α2 - 肾上腺素能受体。
