Development of sensory‐motor synapses in the spinal cord of the frog.

Frank, Eric; Westerfield, Monte

doi:10.1113/jphysiol.1983.sp014912

Cited by 65 publications

(45 citation statements)

References 35 publications

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“…Although it is not clear how this synaptic specificity is encoded, the first stage might involve the same mechanisms that are responsible for determining selectivity at Ia-MN synapses. These synapses are known to be highly specific soon after they form (Frank and Westerfield 1983;Mears and Frank 1997), and it is likely that the selectivity of these synapses is determined by the differential and specific expression of recognition molecules on Ia afferents and MNs (Chen et al 2003). If specific subgroups of Ia INs and MNs expressed a similar cohort of recognition molecules, then their innervation by Ia afferents would be specific as well.…”

Section: Specificity Of Synaptic Connections In the Neonatal Reciprocmentioning

confidence: 99%

Early Postnatal Development of Reciprocal Ia Inhibition in the Murine Spinal Cord

Wang

Li²,

Goulding³

et al. 2008

Journal of Neurophysiology

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Early postnatal development of reciprocal Ia inhibition in the murine spinal cord. J Neurophysiol 100: 185-196, 2008. First published May 7, 2008 doi:10.1152/jn.90354.2008. The pathway mediating reciprocal inhibition from muscle spindle afferents (Ia axons) to motoneurons (MNs) supplying antagonist muscles has been well studied in adult cats, but little is known about how this disynaptic pathway develops. As a basis for studying its development, we characterized this pathway in mice during the first postnatal week, focusing on the projection of quadriceps (Q) Ia axons to posterior biceps-semitendinosis (PBSt) MNs via Ia inhibitory interneurons. Synaptic potentials in PBSt MNs evoked by Q nerve stimulation are mediated disynaptically and are blocked by strychnine, implying that glycine is the major inhibitory transmitter as in adult cats. The specificity of neuronal connections in this reflex pathway is already high at birth; Q afferents evoke inhibitory synaptic potentials in PBSt MNs, but afferents supplying the adductor muscle do not. Similar to this disynaptic pathway in cats, Renshaw cells inhibit the interposed Ia interneurons, as they reduce the disynaptic input from Q axons but do not inhibit PBSt MNs directly. Reciprocal inhibition functionally inhibits the monosynaptic excitatory reflex in PBSt MNs by P3, but this functional inhibition is weak at P1. Finally, deletion of the transcription factor Pax6, which is required for the development of V1-derived Renshaw cells, does not block development of this pathway. This suggests either that Pax6 is not required for the phenotypic development of all V1-derived spinal interneurons or that these inhibitory interneurons are not derived from V1 precursors.

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Section: Specificity Of Synaptic Connections In the Neonatal Reciprocmentioning

confidence: 99%

Early Postnatal Development of Reciprocal Ia Inhibition in the Murine Spinal Cord

Wang

Li²,

Goulding³

et al. 2008

Journal of Neurophysiology

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“…The synchronization and amplification of motoneurone activity'through electrical coupling may play a role in the specification of synapse formation. One disadvantage of the hypothesis that neuronal activation plays a role in synaptic specificity has been that stretch receptors of both agonist and antagonistic muscles are activated during muscle contraction (see Frank & Westerfield, 1983). An answer to this rests on two points: (1) that the electrical coupling of functionally related motoneurones would assure a uniform response to a synaptic input and (2) that it has been shown in the inferior olive that the efficacy of an input depends on the part of the oscillatory cycle, trough or peak, during which the signal reaches the cell ensemble (Llinas & Sasaki, 1989).…”

Section: Synaptic Specificitymentioning

confidence: 99%

Postnatal changes in motoneurone electrotonic coupling studied in the in vitro rat lumbar spinal cord.

Walton

Olivares-Navarrete

1991

The Journal of Physiology

180

138

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SUMMARY1. Electrotonic coupling between motoneurones innervating ankle flexor and extensor muscles, as well as between unidentified lumbar motoneurones, was studied using intracellular recordings in an in vitro spinal cord-hindlimb preparation isolated from rats between birth (PO) and 13 days (P13).2. Graded ventral root stimulation could elicit graded, short latency depolarizations (SLD) which preceded, coincided with, or followed the antidromic action potential. These SLDs were identified as electrotonic junctional potentials by their latency, relative insensitivity to changes in membrane potential and their resistance to one or more of the following: (1) high-frequency stimulation, (2) collision with a somatofugal action potential, (3) removal of Ca2+ from the bathing solution.3. SLDs were studied in 162 neurones and were identified in 77-2 % of the cells in preparations from P0 to P3 rats (n = 57), but only in 30-8 % at P8 to P13 (n = 39).4. SLDs were largest in the youngest animals (P0 to P3), decreasing from a mean of 1-31 mV (±0-17, n = 34) to 0-56 mV (±010, n = 7) at P8 to P13. The SLDs comprised two to eight (4-3+0±36) all-or-none components as determined from twenty collision experiments.5. Electrotonic coupling between motoneurones was specific. SLDs could be elicited in given motoneurones by stimulation of their homonymous but never of their antagonistic muscle nerves.6. These results indicate that electrotonic coupling between lumbar motoneurones in neonatal animals exhibits a high degree of specificity and that its significance, as judged by the amplitude and frequency of occurrence of SLDs, decreases postnatally at a rate that can be correlated with the functional maturity of the motoneurones and the muscular system.

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“…Metamorphosis involves considerable alterations in body morphology, peripheral and central nervous system structures, and behaviors (1,2). This process has been studied extensively in several neural systems, particularly visual, motor, and lateral line systems (3)(4)(5)(6)(7). Little is known about the development of central auditory system function across metamorphosis (6)(7)(8) even though acoustic cues play a paramount role in regulating social behaviors in adult frogs (9).…”

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confidence: 99%

Transient “deafness” accompanies auditory development during metamorphosis from tadpole to frog

Boatright-Horowitz

Simmons

1997

Proc. Natl. Acad. Sci. U.S.A.

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During metamorphosis, ranid frogs shift from a purely aquatic to a partly terrestrial lifestyle. The central auditory system undergoes functional and neuroanatomical reorganization in parallel with the development of new sound conduction pathways adapted for the detection of airborne sounds. Neural responses to sounds can be recorded from the auditory midbrain of tadpoles shortly after hatching, with higher rates of synchronous neural activity and lower sharpness of tuning than observed in postmetamorphic animals. Shortly before the onset of metamorphic climax, there is a brief ''deaf'' period during which no auditory activity can be evoked from the midbrain, and a loss of connectivity is observed between medullary and midbrain auditory nuclei. During the final stages of metamorphic development, auditory function and neural connectivity are restored. The acoustic communication system of the adult frog emerges from these periods of anatomical and physiological plasticity during metamorphosis.Many species of anuran amphibians undergo a developmental process called metamorphosis, during which the aquatic larval tadpole transforms into a partly terrestrial frog. Metamorphosis involves considerable alterations in body morphology, peripheral and central nervous system structures, and behaviors (1, 2). This process has been studied extensively in several neural systems, particularly visual, motor, and lateral line systems (3-7). Little is known about the development of central auditory system function across metamorphosis (6-8) even though acoustic cues play a paramount role in regulating social behaviors in adult frogs (9). We report here physiological work characterizing neural responses to sounds in a central auditory nucleus during the period of neuroanatomical rearrangement across the transition from tadpole to frog.Stages of metamorphosis are classified according to changes in body morphology in the posthatching period (10). Premetamorphic animals (stages 25-30) have no or rudimentary external hind limb buds. Early prometamorphic animals (stages 31-37) show emerging hind limb buds at different degrees of differentiation. Tadpoles in these early stages have neither an external tympanum nor an extratympanic opercularis system for sound conduction to the inner ear organs, and there are several hypotheses regarding the identity of a potential acoustic pathway in these animals (11-13). Late prometamorphic animals (stages 38-41) show final stages of external hind limb differentiation and internal development of forelimbs. By stage 41, the extratympanic sound conduction pathway operating in adults (which includes the opercularis muscle and the operculum cartilage, connecting the shoulder girdle to the oval window in the inner ear) has developed (11). Animals in metamorphic climax (stages 42-45) show emergence of forelimbs, degeneration of the tail, and remodeling of the head, including loss of the oral disk, broadening of the mouth, and change in eye position. The lateral line system has degenerated by climax. I...

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Development of sensory‐motor synapses in the spinal cord of the frog.

Cited by 65 publications

References 35 publications

Early Postnatal Development of Reciprocal Ia Inhibition in the Murine Spinal Cord

Early Postnatal Development of Reciprocal Ia Inhibition in the Murine Spinal Cord

Postnatal changes in motoneurone electrotonic coupling studied in the in vitro rat lumbar spinal cord.

Transient “deafness” accompanies auditory development during metamorphosis from tadpole to frog

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