Dorsal Root Potentials of the Spinal Cord

Presynaptic action of barbiturates in the frog spinal cord.

“…3D), and a comparison of curves of current against potential in the presence and absence of pentobarbital suggests that the reversal potential for the pentobarbital depolarization is similar to that for GABA (27); in Fig. 2E (15)(16)(17)(18)(19)33) and would be expected to contribute to the depression of sensory input. This enhancement in the presence of barbiturates could result from the prolonged release of GABA (and possibly taurine), substances proposed as transmitters mediating presynaptic inhibition (23)(24)(25)(26)(27), an inhibition in the uptake or catabolism of these substances from the synaptic cleft (29), or an enhancement of the action of the transmitter.…”

“…The available evidence suggests that the barbiturates act mainly at synapses, suppressing excitatory synaptic transmission (1)(2)(3)(4)(5)(6)(7)(8) and usually either preserving or augmenting inhibitory synaptic transmission (6,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). The action of barbiturates on the spinal monosynaptic pathway has received the most rigorous analysis, and it has been shown that, in low doses, they reduce the amount of transmitter released from the primary afferents (4 The pH of the drug solutions was adjusted when necessary with NaOH or HCl.…”

Potential changes recorded inside primary afferent fibres within the spinal cord

“…The potentials relevant to the present study have been recorded, either by various dispositions of electrodes on the dorsum of the cord (Gasser & Graham, 1933;Bernhard, 1952Bernhard, , 1953Bernhard & Widen, 1953;Austin & McCouch, 1955;Koketsu, 1956b), or within it (Eccles, Fatt, Landgren & Winsbury, 1954; Coombs, Curtis & Landgren, 1956; Koketsu, 1956 a, b;Fernandez de Molina & Gray, 1957), or by electrodes on the dorsal roots which have been dissected up to the point of entry into the spinal cord and then raised up into an insulating medium, air or oil (Barron & Matthews, 1938;Fessard & Matthews, 1939;Bonnet & Bremer, 1938Woolsey & Larrabee, 1940;Eccles & Malcolm, 1946;Bremer & Bonnet, 1949;Lloyd & McIntyre, 1949;Lloyd, 1952;Brooks & Fuortes, 1952; Malcolm, 1953;Eisenman & Rudin, 1954;Brooks & Koizumi, 1956). …”

Sodium and the dorsal root potential

“…Initially it was thought that the depolarization results from ionic changes persisting in the region of the terminals after activity and is similar to the negative after-potential of peripheral nerve fibres. Subsequent investigators demonstrated synaptic properties of the process generating the DRP and suggested that internuncial neurones are concerned in its generation (Eccles & Malcolm, 1946;Lloyd & McIntyre, 1949). The role of the small cells of the substantia gelatinosa and the Lissauer tract in its generation and transmission has been shown (Wall, 1962).…”