Recurrent Facilitation of Frog Motoneurons

Electrical interaction between antidromically stimulated frog motoneurones and dorsal root afferents: enhancement by gallamine and TEA

“…The VR-VRP appears to be the sign of electrical interaction between dendritic fields of adjacent motoneurones (Grinnell, 1966). It is excitatory, summing with orthodromic EPSPs to increase depolarization of motoneurones (Kubota & Brookhart, 1963;Grinnell, 1966;Meij et al 1968 Gallamine quickly blocks the late VR-DRP, consistent with its role as a peripheral neuromuscular blocking agent and the accumulated evidence that the interaction involves a cholinergic synapse (Eccles & Malcolm, 1946;Kiraly & Phillis, 1961;Grinnell, 1966). This block could be overcome in certain instances by raising Ca2+ to 20 mm.…”

“…There was no comparable occlusion or long term facilitation following tetanic stimulation of the VR, and post-tetanic potentiation of the DR-DRP was not seen. (Kubota & Brookhart, 1963;Grinnell, 1966). Similar attempts were made to affect the early VR-DRP by strongly polarizing or depolarizing dorsal root fibres where they entered mineral oil close to the cord.…”

A study of spontaneous miniature potentials in spinal motoneurones

“…21 show an intracellular example of the dorsal root potential ('antidromic DRP') which arises, in the frog, some 20 msec (100 C) after the firing of a ventral root volley. Figure 3 illustrates a less familiar effect, namely a response of the motoneurone to antidromic impulses in other motor axons observed also by Kubota & Brookhart (1962). It occurs after a much shorter latency (2-2.5 msec) than the DRP, but there is no doubt that it is due to a synaptic depolarizing action.…”

Anurans

“…Stimulation of a ventral root leads to impulse activity in neighbouring ventral roots (Washizu 1960;Grinnell 1966). Direct synaptic interactions among frog motoneurons have been demonstrated by intracellular recording (Katz and Miledi 1963;Kubota and Brookhart 1963;Grinnell 1966;Matsuura 1971;Westerfield and Frank 1982;Shapovalov and Shiriaev 1984b), HRP tracing (Erulkar and Soller 1980) and Lucifer Yellow dye-coupling (Adanina et al 1983). Intracellular injection of the fluorescent dye Lucifer Yellow into single motoneurons of the isolated perfused frog (Rana ridibunda) spinal cord resulted in backfilling of presynaptic fibres originating from dorsal roots and ventrolateral funiculi (Adanina et al 1983).…”