Relationship between central perceptivity of noradrenalin and oral dryness

穹窿下器官（SFO）的激活诱导饮酒行为，即口腔干燥。本研究采用全细胞膜片钳技术，观察了NA及其类似物对大鼠脑片SFO神经元的作用。在电流钳模式下，10-100 μM NA的应用产生膜去极化（63%，17个反应神经元/27个测试的神经元）和超极化（22%，6/27个神经元）。在电压钳模式下，施加1-100 μM的NA产生内向电流（69%，42/61个神经元）和外向电流（23%，14/61个神经元）。这些电流仍然存在TTX或在谷氨酸和GABA受体拮抗剂的共同应用。在大多数神经元（25/31）显示内向电流在NA的存在下，膜电导没有改变电压斜坡或超极化脉冲刺激。通过应用α 1激动剂苯乙哌啶也获得了类似的反应。α1受体拮抗剂哌唑嗪可抑制苯肾上腺素诱发的内向电流。此外，α2激动剂可乐定降低自发GABA能抑制性突触后电流的频率（4/10个神经元）。结果提示，大鼠SFO神经元通过α1肾上腺素能受体在突触后被激活，抑制突触前α2肾上腺素能受体的GABA能抑制性突触输入可增强这种激活。

Activation of the subfornical organ (SFO) induces drinking behavior, that is, oral dryness. In this study, the effects of NA and its analogues on SFO neurons in rat slice preparations were investigated by using whole cell patch clamp recording. In the current clamp mode, the application of NA at 10-100 μM produced membrane depolarization (63%, 17 responsive neurons /27 neurons tested) and hyperpolarization (22%, 6/27 neurons). In the voltage clamp mode, NA application at 1-100 μM produced inward currents (69%, 42/61 neurons) and outward currents (23%, 14/61 neurons). These currents were remained in the presence of TTX or in the coapplication of glutamate and GABA receptor antagonists. In most of the neurons (25/31 neurons) showing inward currents in the presence of NA, the membrane conductance was not changed by voltage ramps or hyperpolarizing pulse stimulation. Similar responses were obtained by the application of the αl agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the α1 antagonist prazosin. In addition, the α2 agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). The results suggest that SFO neurons in rats are activated postsynaptically through α1 adrenoceptors, and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic α2 adrenoceptors.