1. Synaptic transmission Module 725 Lecture 2

2. Aim nWhy do we need synapses? nTo know about chemical synapses u diversity u flexibility u mechanisms

3. Overview nNeurotransmitters nSynaptic structure nTransmitter release nTransmitter breakdown/uptake nIonotropic receptors

4. Neurotransmitters nAcetylcholine namino-acids u glutamate u GABA npeptides u FMRFamide nNO (see next week)

5. Synaptic structure nNeuromuscular junction nCNS synapses nCommon features u transmitter stored in vesicles u receptors on post- synaptic membrane u cell-cell signalling to organise synapse

6. Neuromuscular junction

7. CNS synapses

8. Overview of physiology nSimulation at http://lessons.harveyproject.org/developm ent/nervous_system/cell_neuro/synapses/ release.html

9. Transmitter release ncalcium-dependent nvesicle cycling - or kiss and run

10. Calcium domains nsquid giant synapse nuse n-aequorin-J as Ca indicator

11. Calcium-dependency nCalcium entry very near vesicle! nmicro or even nano-domains nsynaptotagmin as Ca sensor ?

12. Vesicle cycling nConventional view nneed recycling because no evidence of increase in membrane area u e.g. capacitance measurements

13. Vesicle proteins nsynaptobrevin & SNAP-25 anchor vesicle membrane to plasma membrane nsyntaxin helps in conformational change nsynaptotagmin as Ca sensor

14. Synaptotagmin ncalcium sensor u arginine in C 2 A and C 2 B domains

15. Exocytosis nfree energy barriers need to be overcome during fusion

16. Endocytosis nClathrin coats “empty” vesicles Movie from http://www.hms.harvard.edu/news/clathrin/

17. Kiss and run

18. testing… testing... ncapacitance measurements- measures surface area nGFP-derivative called synaptophlorin reports pH (vesicles very acid) nFM dye which fluoresces only in membrane

19. Summary so far ntransmitter put into vesicles nvesicle release is Ca-dependent nmajor protein players include u synaptotagmin u SNARE u clathrin

20. Breakdown or uptake? nesterase (ACh, peptides) ntransport - mostly into glia (amino acids)

21. Re-uptake n12 membrane spanning regions nco-transport using Na gradient

22. Uptake inhibitors nmajor drugs u cocaine - block serotonin & dopamine reuptake u Prozac - selective serotonin reuptake inhibitors serotonin cocaine prozac

23. Summary so far ntransmitter put into vesicles nvesicle release is Ca-dependent ntransmitter recycled u after breakdown u direct pump for reuptake

24. Ionotropic receptors nIonotropic receptors have an integral channel which opens when receptor binds nMetabotropic receptors activate a second messenger internally nImportant ionotropic receptors include u nicotinic ACH receptor u glutamate (NMDA, AMPA, Kainate) u GABA

25. Nicotinic ACh receptor 2 , one each of  ,  ACh binds to  - need 2 ACh to open channel

26. Nicotinic ACh receptor nhighly conserved residues binding ACh

27. Glutamate receptor 2 , one each of  ,  glu binds to  - need 2 glu to open channel nNMDA receptors also need glycine

28. Multiple glu receptors nNamed after agonists

29. NMDA receptors (I) nblocked by Mg, except at depolarised voltages nneed glycine as cofactor squirt a-a and see cell current

30. NMDA receptors (II) nmay provide slow component to synapse stimulate presynaptic neuron and see cell current

31. AMPA & Kainate receptors nMay both be used at same synapse nstimulate presynaptic cell and record voltage u APV blocks NMDA, GYKI blocks AMPA LY293558 blocks kainate

32. GABA A receptor

33. GABA A - drug action nBenzodiazepines e.g. Valium (=diazepam) u hypnotic, anxiolytic, anticonvulsant, myorelaxant and amnesic n Barbiturates e.g. pentobarbital u sedative action

34. GABA A - diazepam nlonger openings in bursts control DZ

35. Summary ntransmitter put into vesicles nvesicle release is Ca-dependent ntransmitter recycled u after breakdown u direct pump for reuptake nionotropic receptors u great diversity u homologous subunits nSynaptic transmission major drug target