Ch. 5 Synaptic transmission Electrical synapse Chemical synapse 雙向 快速

Electrical synapse: to synchronize electrical activity among populations of neurons (hypothalamus) crayfish 小龍蝦 ATP, c-AMP

Chemical synapse AP voltage-dependent Ca2+ channels

Quantal transmission at neuromuscular synapses End plate potential (EPP) spontaneous changes occur in muscle cell mambrane miniature end plate potentials (MEPPs): occur even in the absence of stimulation, block by curare (ACh receptor blocker) EPP = summation of MEPPs Low Ca2+ EPP fluctuations

假說：these “quantal” fluctuations suggest that EPPs are made up of individual units, each equivalent to a MEPP 驗證：independent occurrence of unitary events (Poisson statistics): predict the distribution of EPP amplitudes 結論：presynaptic AP causes a postsynaptic EPP because it synchronizes the release of many transmitter quanta

Release of transmitters from synaptic vesicles: one synaptic vesicle is one MEPP Fusion of synaptic vesicles with the presynaptic membrane 4-AP 會影響 AP 的 duration-> Ca2+

Dock: two membranes become tightly associated with each other prime: active fusion of the membranes

The role of Ca2+ in transmitter secretion 有五種實驗證明 nerve terminal 有 voltage dependent Ca2+ channels 存在：(1) Na+ channels blocker (2) voltage clamp experiment 如圖所示 (3) Ca2+ imaging 如下圖 (4) 直接打入 Ca2+ (5) Ca2+ chelators The purpose of AP is to activate Ca2+ channels -latrotoxin triggers Ca2+ independent exocytosis Ca2+ channel blocker 鎘 Block Na+ & K+ channels

Fura-2 在 presynaptic neuron 打入 Ca2+ Ca2+ chelators

Synaptotagmin: Ca2+ sensor, bind to neurexins NSF & SNAP: common proteins in fusion, 與 SNARE 結合 (SNAP receptors 包括 synaptobrevin, syntaxin& SNAP-25)

Toxins that affect transmitter release Clostridial toxins (梭狀芽孢桿菌毒素), botulism (肉類桿菌中毒), tetanus (破傷風) botulinum toxin & tetanus toxin: cleave synaptobrevin, syntaxin & SNAP-25 female black widow spider: -latrotoxin triggers Ca2+-independent exocytosis, bind to neurexins

Ch. 6 Neurotransmitters The utility cycle of all neurotransmitters: (1) synthesized & packaged (2) release & binding (3) removed or degraded classified into tow broad categories: (1) small-molecule NMs (2) neuropeptide

What defines a neurotransmitter? 1926, Otto Loewi Vagus nerve Heart rate Heart rate “vagus substance” ACh

Criteria that define a substance as a neurotransmitter: Box A 斜體字

The comparisons of neurotransmitters to hormones Action at a distance vasopressin, oxytocin, can be as a hormone and as a NM

Two major categories of neuro-transmitters (1)small-molecule neurotransmitters: ATP, AMP (2) peptide neurotransmitters

請任舉兩個實驗證明 nevre terminal 具有 voltage- dependent Ca2+ channels。 請說明 Otto Loewi 證明神經傳導物質存在的實驗。