Postsynaptic Potentials in Toad's Spinal Motoneurons Due to Muscle Afferent Volleys

Abstract

Although some investigators are dubious of a direct connection between the

The Morphology of Spinal Afferent-Efferent Relationships in Vertebrates

“…A number of physiological studies have demonstrated the existence of a segmental monosynaptic reflex in amphibians [Araki, 1960;Fadiga and Brookhart, 1960;F ukami, 1961; H olemans ei a/., 1966; among others]. These studies have suggested that this linkage is principally, if not solely, of an axodendritic character.…”

“…In this light, the neuroanatomical relationships which have been described in the pres ent investigation may explain certain electrophysiological findings. It has been reported [Araki, 1960;Fadiga and Brookhart, 1960;F ukami, 1961;and H olemans et ai, 1966] that the excitatory postsynaptic poten tials generated directly in amphibian motoneurones by primary afferent fibers only infrequently result in motoneuronal activation. On the other hand, dorsal root stimulation in cat [e.g., Lloyd, 1943] and primates [e.g., P reston and W hitlock, 1960] usually generates monosynaptic ac tivation of motoneurones.…”

The Ionic Mechanisms of Excitatory and Inhibitory Synaptic Action

“…It appears that the same ionic mechanism is responsible for the IPSPs of other central synapses because, like motoneuronal IPSPs, they are readily converted to depolarizing responses by the diffusion of chloride out of an intracellular KC1 microelectrode. The following list gives neurones in which the IPSPs are inverted in this manner: the cells of origin of the dorsal spinocerebellar tract (Curtis et al, 1958); hippocampal pyramidal cells (Kandel et al., 1961; Andersen et id., 1964a); cells of the cuneate nucleus (Andersen et al, 1964b); Purkinje cells of the cerebellum (Eccles et al, 1965); pyramidal cells of the neocortex (Stefanis & Jasper, 1964); toad motoneurones (Fukami, 1961 ); Mauthner cells of fish (Asada, 1963).…”

Conduction and Transmission in the Nervous System

“…There is agreement that inhibitory postsynaptic potentials in frog moto neurons are mediated through oligosynaptic pathways (73,120). The same conclusion is reached about cat motoneurons, where the synaptic delay for excitatory and inhibitory synapses is the same (61).…”