Dorsal root reflexes of muscle Group I afferent fibres

Eccles, John C.; Kozak, W; Magni, F.

doi:10.1113/jphysiol.1961.sp006797

Cited by 113 publications

(87 citation statements)

References 23 publications

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“…11 L. When the stimulus to the GS nerve was weakened so that it virtually excited only Group Ia afferent fibres ( Fig. 12A-E), the proportional depression of the gastrocnemius afferent volley was greater, as reported in the previous paper (Eccles et al 1961), but it was still less than the EPSP depression. Evidently in Fig.…”

Section: Time Course Of Epsp Depressionsupporting

confidence: 69%

“…F-I resemble Fig. 11 A-H, F being the control and G-I at the test intervals indicated in msec, except that the frequency of repetition was raised to 5/sec, so as virtually to eliminate complications due to dorsal root reflexes (Eccles et al 1961). Measurements from the series partly illustrated in F-I are plotted in J with the same conventions as in E. Further explanation in text.…”

Section: Time Course Of Epsp Depressionmentioning

confidence: 97%

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Central inhibitory action attributable to presynaptic depolarization produced by muscle afferent volleys

Eccles¹,

Eccles²,

Magni³

1961

The Journal of Physiology

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386

215

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Section: Time Course Of Epsp Depressionsupporting

confidence: 69%

Section: Time Course Of Epsp Depressionmentioning

confidence: 97%

Central inhibitory action attributable to presynaptic depolarization produced by muscle afferent volleys

Eccles¹,

Eccles²,

Magni³

1961

The Journal of Physiology

Self Cite

386

215

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“…(2) EPSP-triggered averaging revealed that the action potentials propagate not only antidromically in the DRs but also centrally and that they trigger EPSPs in MNs. In agreement with these observations, DR reflexes in group Ia afferents have been shown in cats not only to propagate distally but also to release transmitter centrally (and thus to evoke EPSPs in MNs) and even to cause large reflex discharges under certain experimental conditions (for review, see Willis, 1999;Eccles et al, 1961;Eccles and Willis, 1963). (3) Surprisingly, potentiating GABAergic antidromic discharges by diazepam increased the EPSPs recorded from MNs, and, conversely, blocking DR bursts by PTX markedly reduced these EPSPs, demonstrating that similar mechanisms are involved.…”

Section: Discussionsupporting

confidence: 52%

Primary Afferent Terminals Acting as Excitatory Interneurons Contribute to Spontaneous Motor Activities in the Immature Spinal Cord

Bos¹,

Brocard²,

Vinay³

2011

Journal of Neuroscience

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Patterned, spontaneous activity plays a critical role in the development of neuronal networks. A robust spontaneous activity is observed in vitro in spinal cord preparations isolated from immature rats. The rhythmic ventral root discharges rely mainly on the depolarizing/ excitatory action of GABA and glycine early during development, whereas at later stages glutamate drive is primarily responsible for the rhythmic activity and GABA/glycine are thought to play an inhibitory role. However, rhythmic discharges mediated by the activation of GABA A receptors are recorded from dorsal roots (DRs). In the present study, we used the in vitro spinal cord preparation of neonatal rats to identify the relationship between discharges that are conducted antidromically along DRs and the spontaneous activity recorded from lumbar motoneurons. We show that discharges in DRs precede those in ventral roots and that primary afferent depolarizations (PADs) start earlier than EPSPs in motoneurons. EPSP-triggered averaging revealed that the action potentials propagate not only antidromically in the DR but also centrally and trigger EPSPs in motoneurons. Potentiating GABAergic antidromic discharges by diazepam increased the EPSPs recorded from motoneurons; conversely, blocking DR bursts markedly reduced these EPSPs. High intracellular concentrations of chloride are maintained in primary afferent terminals by the sodium-potassium-chloride cotransporter NKCC1. Blocking these cotransporters by bumetanide decreased both dorsal and ventral root discharges. We conclude that primary afferent fibers act as excitatory interneurons and that GABA, through PADs reaching firing threshold, is still playing a key role in promoting spontaneous activity in neonates.

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“…to dorsal root reflexes, and the subsequent monosynaptically evoked depolarization of motoneurones instead of the activation of interneurones between I a afferents and motoneurones. Eccles, Kozak & Magni (1961) found that the dorsal root reflexes resulting from electrical stimulation of group I afferents never had a segmental latency less than 4 msec. In a separate series of observations we have measured the latency for such reflexes in preparations treated with 4-aminopyridine, which may shorten their latency (Jankowska, Lundberg, Rudomin & Sykova, 1977), and found similar minimum values.…”

Section: Methodsmentioning

confidence: 99%

Oligosynaptic excitation of motoneurones by impulses in group Ia muscle spindle afferents in the cat

Jankowska¹,

McCrea²,

Mackel³

1981

The Journal of Physiology

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SUMMARY1. Intracellular recording from hind-limb motoneurones was used to investigate whether di-and trisynaptic (oligosynaptic) excitatory post-synaptic potentials (e.p.s.p.s) are evoked from group Ia muscle spindle afferents in those motoneurones in which such potentials are evoked from I b tendon organ afferents or entire group I afferents. I.a afferents of triceps surae and plantaris were activated either selectively by single brief stretches of these muscles, or together with Ib afferents by electrical stimuli applied to the nerves.2. Muscle stretches below threshold for lb afferents (10-35,um) evoked e.p.s.p.s which appeared with latencies compatible with disynaptic and trisynaptic coupling between the afferents and the motoneurones. The latencies of a majority of these e.p.s.p.s were too short to allow their mediation by group II afferents, if any were activated by the applied stretches. They were also too short to be compatible with effects attributable to dorsal root reflexes. These e.p.s.p.s are thus attributed to oligosynaptic actions of Ia afferents.3. Stretch-evoked di-and trisynaptic I a e.p.s.p.s were found in 83 % of motoneurones in which e.p.s.p.s were evoked by stimuli which activated both Ia and lb afferents; in five motoneurone species they were found in more than 90 %. These observations lead to the conclusion that group I a muscle spindle afferents evoke not only inhibitory but also excitatory actions in parallel with group lb tendon organ afferents.4. The distribution of Ia oligosynaptic stretch-evoked excitation from ankle and toe extensor muscles was compared with the distribution of Ia non-reciprocal inhibition as described by Jankowska, McCrea & Mackel (1981b). Excitation predominated in posterior biceps-semitendinosus motoneurones and inhibition in other species of motoneurones investigated, except those of intrinsic foot muscles (tibial motoneurones); similar proportions of the latter showed excitation and inhibition.

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Dorsal root reflexes of muscle Group I afferent fibres

Cited by 113 publications

References 23 publications

Central inhibitory action attributable to presynaptic depolarization produced by muscle afferent volleys

Central inhibitory action attributable to presynaptic depolarization produced by muscle afferent volleys

Primary Afferent Terminals Acting as Excitatory Interneurons Contribute to Spontaneous Motor Activities in the Immature Spinal Cord

Oligosynaptic excitation of motoneurones by impulses in group Ia muscle spindle afferents in the cat

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