神经元之间的信息传递
(Synaptic Transmission Between Neurons)
薛冰 北京大学神经科学研究所
神经元之间信息传递的方式
v 神经元最主要的功能是通过突触(Synapse)进行细胞间的信息传递 v 突触有电突触(Electrical Synapse)和化学性突触(Chemical Synapse)
Direction of transmission
Electrical Synapse
3.5 nm
Yes
Gap-iunction channels Ion current Virtually absent
Usually bidirectional
Chemical Synapse
20 - 40 nm
No Presynaptic vesicles and active zones; postsynaptic receptors
v 递质释出后经突触间隙作用于后膜上特异受体而发挥 其生理效应
v 存在使该递质失活的酶或其他方式(如重摄取)
v 有特异的受体激动剂或拮抗剂，并能够分别拟似或阻 断该递质的突触传递作用
递质的分类(Categories of neurotransmitters)
v 经典神经递质(Classical neurotransmitters) 》
Chemical transmitter Significant:at least 0.3 ms, usually 1- 5 ms or longer
unidirectional
Current flows differently at electrical and chemical synapses
S型
F型
按突触功能分类
兴奋型
抑制型
神经递 质(Neurotransmitter)
—在化学性突触传递过程中起信息传递作用的化学物质
神经递质的判定标准（ Criteria for neurotransmitter）
v 突触前神经元存在合成递质的前体和酶体系，并能合 成该递质
v 递质存在突触小泡内，当冲动抵达末梢时，小泡内递 质能释放入突触间隙
¬ Postsynaptic Receptors Gate Ion Channels Either Directly or Indirectly
§ Ligand-gate Ion Channel Receptors § G-protein coupled Receptors (Second-Messenger Pathways) § Tyrosine Protein Kinase Receptors
Neurotransmitters act either directly or indirectly on ion channels that regulate current flow in neurons
突触的分类
Hale Waihona Puke 按突触膜的特征分类Gray
Ⅰ型
Ⅱ型
Colonnier 不对称型 对称型
按突触小泡的形态分类(Uchizon&Bodian)
Electrical Synapses
v Gap-Junction Channels Connect Communicating Cells at an Electrical
Synapse
v Electrical Transmission Allows the Rapid and Synchronous Firing of
，但以化学性突触为主
v 电突触通过缝隙连接(gap junction)直接完成细胞间的电信息传递Fig.1
v 化学性突触传递必须依赖于神经递质(Neurotransmitters)或神经肽
(Neuropeptides)作用于突触后膜的受体而完成细胞间的信息传递Fig.2
Fig. 1
Current flows at electrical synapse
Chemical Synapses
v How do Signals from Pre-synaptic Cell Transmit to Post-synaptic Cell ? － Electrical-Chemical-Electrical Signals Transform
Ø Releases of Chemical Transmitters from Pre-synaptic Membrane Ø Chemical Transmitters Bind to Postsynaptic Receptors
Interconnected Cells
v Electrical Synapses Provide Instantaneous Signal Transmission
v Electrical Synapses are bidirectional
Return
Fig. 2
Distinguishing Properties of Electrical and Chemical Synapses
Distance between pre- and postsynaptic cell membranes Cytoplasmic continuity between pre- and postsynaptic cells Ultrastructural components
Agent of transmission Synaptic delay
v 神经肽(Neuropeptides) 》 v 其它类型
• NO、CO • 组织胺(Histamine) • 腺苷(ATP)》
经典神经递质(Classical neurotransmitters)
Ø 乙酰胆碱(Acetylcholine, Ach)
Ø Open or Close of Postsynaptic Ion Channels － Postsynaptic Potentials －Action Potentials of Postsynaptic cell
Synaptic transmission at chemical synapses involves several steps