Excitatory Postsynaptic Responses to Presynaptic Impulses

Abstract

With excitatory synapses it has been an invariable finding that presynaptic impulses evoke a localized depolarization of the postsynaptic membrane. With neuronal synapses this response has been termed the excitatory post-synaptic potential (EPSP), and, with neuromuscular synapses, the endplate potential (EPP). In the earlier investigations the EPSP and EPP were observed by extracellular recording (Göpfert and Schaefer 1938; Schaefer and Haassr 1939; Eccless and O’Connor 1938, 1939; Feng 1940; Eccless and Kuffler1941; Eccless, Katz and Kuffler 1941; Kuffler 1942 a, b; Books and Eccless 1947B; Bullock 1948; Bishop 1953), or by recording the potential electrotonically propagated along the postsynaptic axons, for example from the postganglionic trunk of a sympathetic ganglion (Eccless 1935, 1943) or from ventral roots of the spinal cord (Barron and Matthews 1936, 1938; Eccless and Pritchard 1937; Eccless 1946a). But these older techniques are almost completely superseded by the intracellular recording of post-synaptic potentials, which was first applied to the neuromuscular synapses (Fatt and Katz 1950, 1951a, 1952a; Nastuk 1953) then to the following structures: the mammalian motoneurone (Brock, Coombs and Eccless 1951, 1952; Woodbury and Patton 1952; Frank and Fuortes 1955); the motoneurones of the electric lobe of Torpedo (Albe-Fessard and Buser 1952, 1954); the motoneurones of the toad spinal cord (Araki, Otani and Furukawa 1953; Araki and Otani 1955); the crustacean neuromuscular synapses (Fatt and Katz 1953A); the stellate ganglion of Loligo (Bullock and Hagiwara 1955); the mammalian sympathetic ganglion (R. M. Eccles 1955); the giant ganglion cells of Aplysia (Tauc 1955); to quote most of the pioneer investigations performed up to 1955. More recent investigations will be re-viewed when the many features of excitatory synaptic action are considered under the various headings.