Signal processing/integration (AP, dendrites) 3 1 2 Signal processing/integration (AP, dendrites) Output (vesicle release, AP-release coupling) Input (single channel, whole cell currents, chemical synapses)

U R = I τ = R·C Basics resistance capacitor Ion channels vs. pumps Resistive capacitive components Reversal- and membrane potential

Basics Number of neurons in the human brain: ~8.5·1010 Dudok Barna, Katona lab Number of neurons in the human brain: ~8.5·1010 Number of synapses in the human brain : 1014-1015 Number of neurons in the human neocortex: ~2·1010

Signal processing/integration (AP, dendrites) 3 1 2 Signal processing/integration (AP, dendrites) Output (vesicle release, AP-release coupling) Input (single channel, whole cell currents, chemical synapses)

Neuronal signal processing AD/DA converter dendrites axon initial segment axon

τ = R·C Analogue signal propagation RC circuit cabel-theory τ = rmcm áram feszültség  τ = rmcm τ = R·C

τ = R·C Analogue signal propagation RC circuit Rectifycation (active components) áram feszültség áram feszültség τ = R·C

Voltage clamp IM = Iion + Icap Icap = cm · dV dt A. L. Hodgkin A.F. Huxley Nobel Prize in Physiology, 1963

Na+ és K+ currents during the AP Measured ionic currents Theoretical currents/conductance

Single channel patch clamp Hamill et al., 1981 Erwin Neher, Bert Sakmann Nobel Prize in Physiology, 1991

Single channel patch clamp Hamill et al., 1981 Im

Ionic channels Na+ channels: fast activation, inactivation K+ channels: delayed

Structural similarity: 4x6TM S5-S6 domain: „water” pore, selectivity S1-S4domain: votlage-dependency gating S6 and S4-5 link

Voltage-dependence (non linear IV) - S4 domain: 6-7 + charges by Arg, Lys, conformation changes (paddle S4>S1) Selectivity: P-loop

- high Na-channel densitiy - left-shifted V-dependence Axon initial segment: - one per cell - high Na-channel densitiy - left-shifted V-dependence AP initialization Hu et al. Kole et al. Lőrincz & Nusser

Supralinear integration NMDA spike Losonczy & Magee, 2006 dendritic Na+ spikes

Signal processing/integration (AP, dendrites) 3 1 2 Signal processing/integration (AP, dendrites) Output (vesicle release, AP-release coupling) Input (single channel, whole cell currents, chemical synapses)

Quantal release of neurotransmitters Bernard Katz, Nobel Prize in Physiology, 1970

Synaptic vesicle release Change in membrane capacitance = change in membrane surface

Synaptic vesicle release Quantal dye „release”

Synaptic vesicle release James E. Rothman, Randy W. Schekman,Tom Südhof, Nobel Prize in Physiology, 2013

calcium-influx dependent The release is calcium-influx dependent Calcium chelators with different kinetics Calcium sensitive dyes

Signal processing/integration (AP, dendrites) 3 1 2 Signal processing/integration (AP, dendrites) Output (vesicle release, AP-release coupling) Input (single channel, whole cell currents, chemical synapses)

Paired recordings Whole cell patch clamp in vitro brain slice posthoc anatomy CR-GFP CR

Chemical synapses Receptor: ligand-, and ion-selective postsynaptic AMPA MP Outward current= hyperpolarization presynaptic Inward current= depolarization Receptor: ligand-, and ion-selective Ionotropis – Metabotropic receptors Konduktancia változás

Ligand-activated ion channels „Indirect” metabotropic receptors

Specificitás Affinitás Agonsiták/Antagonisták/Alloszterikus modulátorok

Optogenetics

Signal processing/integration (AP, dendrites) 3 1 2 Signal processing/integration (AP, dendrites) Output (vesicle release, AP-release coupling) Input (single channel, whole cell currents, chemical synapses)

Undergrad and “TDK” positions are available for studying hippocampal connectivity and dendritic integration using patch clamp recordings of synaptically connected, anatomically identified neurons, calcium imaging and dendritic and axonal recordings. Contact: szabadics.janos@koki.hu