CHAPTER V 



Synaptic and ephaptic transmission 



HARRY GRUNDFEST 



Department of Neurology, College of Physicians and Surgeons, 

 Columbia University, New York City 



CHAPTER CONTENTS 



Nature of Postsynaptic Potentials 



Generation Sites of Postsynaptic Potentials 



Molecular Structures of Differently Excitable Membranes 



Types of Postsynaptic Potentials 



Interrelations of Postsynaptic Potentials and Spikes 

 Specific Properties of Synaptic Electrogenesis 



Evidence Against Electrical Stimulation of Postsynaptic Po- 

 tentials 



Mechanisms of Bioelectrogenesis 



Other Consequences of Electrical Inexcitability 



a) Sustained electrogenesis 



b) Postsynaptic potentials during hyperpolarization and 

 depolarization 



c) Electrochemical gradation and reversal of postsynaptic 

 potentials 



d) Latency of postsynaptic potentials 



e) Electrotonic effects of presynaptic impulse upon post- 

 synaptic region 



f) Chemical sensitivity of synaptic membrane 

 Postsynaptic Potentials as Nonpropagated Standing' Po- 

 tentials 



Interaction of Graded Responses 

 Events in Synaptic Transmission 



Functional Interrelations Within Single Cell 



Evolution of Electrogenic Membrane 



Transmitter Actions 



Genesis of Postsynaptic Potentials 



Gradation of Postsynaptic Potentials 



Mechanisms of Graded Responsiveness 



Transfer of Activity from Postsynaptic Potentials to Elec- 

 trically Excitable Membrane 



Synaptic Delay 



Superposition of Postsynaptic Potentials and Spikes 

 General and Comparative Physiology of Synapses 



Forms and Magnitudes of Postsynaptic Potentials 



' The researches at the author's laboratory were supported 

 in part by funds from the following sources : Muscular Dys- 

 trophy Associations of America, National Institutes of Health 

 (B-389 C), National Science Foundation and United Cerebral 

 Palsy Associations. 



Cells with Depolarizing Postsynaptic Po- 

 Hyperpolarizing Postsynaptic 



vith 



Postjunctional 

 tentials 



Postjunctional 

 Potentials 



Postjunctional Cells with Both Types of Postsynaptic Po- 

 tentials 



Fast and Slow Responses of Invertebrate Muscles 

 Pharmacological Properties of Synapses and their Physiological 

 Consequences 



Classification of Drug Actions 



Identification and Characterization of Transmitter Agents 



Modes of Action of Transmitter Agents and Synaptic Drugs 



Physiological Implications 



a) Topographic distinctions 



b) Synaptic specificity and transmitters 



c) Reciprocal interactions of neural pathways 



Role of Elementary Synaptic Properties in Integrative Activity 

 Spatial Interrelations of Synaptic and Conductile Membrane 

 Physiological Factors Determining Transmissional Effective- 

 ness 



a) Synaptic potency and drive 



b) Excited and discharged zones 



c) Facilitation 



d) Homosynaptic facilitation 



e) Heterosynaptic facilitation 



f) Spatial summation of converging pathways 

 Integrative Utility of Electrical Inexcitability 

 Synaptic Determinants of Different Types of Reflexes 

 Role of Inhibition in Central Nervous System 

 Physiological Effects of Different Porportions of Depolarizing 



and Hyperpolarizing Postsynaptic Potentials 

 Synaptic Activity and Electrical Concomitants 



a) Interpretations of changes in amplitudes of postsynap- 

 tic potentials 



b) Interpretation of electrotonic effects of standing post- 

 synaptic potentials 



c) Synaptic transducer action and electrogenesis 

 Ephaptic Excitation 



Electrical Modes of Transmission 

 Role of Field Currents in Central Nervous System 

 Dorsal Root Reflex 



Ephaptic Transmission in Annelid and Crustacean Nerve 

 Cords 

 a) Unpolarized ephaptic junctions 



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