一、α肾上腺素能受体的亚型交感神经兴奋时可有两种成份:神经成份为交感神经冲动增加;体液成份为去甲肾上腺素(NE)的释放。当交感神经兴奋时,末梢释放的NE,使突触局部NE浓度增高,激动突触前α-受体,对进一步的NE释放起负反馈调节作用。后发现在突触后的靶器官(如血管平滑肌,突触后的另一神经元)存在另 First, the alpha adrenergic receptor subtypes There are two components of sympathetic activity: the nerve component increases the sympathetic impulse; the body fluid component is the release of norepinephrine (NE). When the sympathetic nerve is excited, peripherally released NE increases the concentration of synaptic NE and activates pre-synaptic a-receptors, with negative feedback regulation of further NE release. After the discovery of post-synaptic target organs (such as vascular smooth muscle, another neuron after the postsynaptic) there are other