CELLULAR NEUROPHYSIOLOGY

Transcription

1 CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND 6. SYNAPTIC INTEGRATION Video 6-1: Compound PSP, PSP propagation and summation

2 Compound postsynaptic potential 2 whole-cell configuration current-clamp mode somatic EPSP + gabazine + APV-CNQX Compound somatic PSP somatic IPSP

3 Excitatory postsynaptic potentials (EPSPs) 3 whole-dendrite configuration current-clamp or voltage-clamp mode current-clamp voltage-clamp

4 EPSP propagation mechanisms 4 whole-cell current-clamp dendritic EPSP (origin, time t0) propagated EPSP (time t1) propagated EPSP (time t2) EPSP propagation is passive and decremental amplitude decreases rise time lengthens

5 EPSP spatial summation 5 Somatic EPSPs linear spatial summation

6 EPSP temporal summation 6 Somatic EPSPs nonlinear temporal summation

7 Take home message 7 EPSPs decrease in amplitude when they passively propagate along dendrites down to the initial segment EPSPs sum up when generated: at similar times at different somato-dendritic locations or at the same location

8 CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND 6. SYNAPTIC INTEGRATION Video 6-2: IPSP propagation and summation

9 Inhibitory postsynaptic potentials (IPSPs) 9 whole-cell current-clamp or voltage-clamp IPSP I GABA Passive and decremental IPSP propagation Linear spatial summation Nonlinear temporal summation

10 10 IPSPs decrease in amplitude when they passively propagate along dendrites down to the initial segment IPSPs sum up when generated: at similar times at different somato-dendritic locations or at the same location

11 CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND 6. SYNAPTIC INTEGRATION Video 6-3: EPSP and IPSP summation

12 EPSPs + IPSPs = compound PPS 11

13 EPSPs + IPSPs: propagation and summation 12 EPSP

14 EPSPs + IPSPs: propagation and summation 13 IPSP

15 EPSPs + IPSPs: propagation and summation 14 EPSP IPSP EPSP + IPSP

16 EPSPs + IPSPs: propagation and summation 15 EPSP

17 EPSPs + IPSPs: propagation and summation 16 IPSP

18 EPSPs + IPSPs: propagation and summation 17 EPSP IPSP EPSP + IPSP

19 Silent inhibition: shunting effect 18

20 19 IPSPs (hyperpolarizations) decrease the amplitude of EPSPs when they sum up by decreasing EPSP amplitude and membrane resistance Silent IPSPs decrease the amplitude of EPSPs when they sum up by decreasing membrane resistance

21 CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND 6. SYNAPTIC INTEGRATION Video 6-4: Roles of postsynaptic potentials

22 PSPs initiate (or do not initiate) action potentials 21 PSP Na + channel -60 mv

23 PSPs initiate (or do not initiate) action potentials mv

24 See How to trigger an action potential (chap. 2) 23 whole-cell current-clamp mode Action potential = strong depolarization sudden short all or none with a threshold potential

25 Overview of postsynaptic integration 25 Inward synaptic currents (e.g.: cations through glutamate receptorchannels) postsynaptic depolarizations (EPSPs) V EPSP = R m I cations Outward synaptic currents (e.g.: chloride ions through GABA A channels) postsynaptic hyperpolarizations (IPSPs) V IPSP = R m I chloride Often E Cl = V m very weak current no IPSP (silent inhibition)

26 Overview of postsynaptic integration 26 Passive propagation EPSPs and IPSPs passively propagate along dendrites their amplitude decreases and their risetime lengthens Linear summation of PSPs PSP sum = geometric sum of EPSPs and IPSPs, when generated far away from each other Non linear summation PSP sum < geometric sum of EPSPs and IPSPs if generated: at close locations on a single dendritic branch or at a single dendritic location multiple times in a row A compound PSP: generates action potentials if its amplitude reaches the Na + channel opening threshold reduces the probability of evoking action potentials if it is hyperpolarizing or silent

27 CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND Professor Constance Hammond Project manager Isabelle Virard Graphic designer Géraldine Fohr Movie director Marine Chabrolin Music Tetoma - Hicham Chahidi Translation Isabelle Virard et Atenao 2016