Electrophysiological and morphological properties of neurons in the ventral horn of the turtle spinal cord

McDonagh, Jan; Gorman, Robert B.; Gilliam, Edwin E.; Hornby, T. George; Reinking, Robert M.; Stuart, Douglas G.

doi:10.1016/s0928-4257(99)80131-4

Cited by 16 publications

(13 citation statements)

References 55 publications

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“…Repeated testing of these cells appeared to have little effect on the steady-state firing rates for 10-30 seconds of stimulation ( Fig. 3E; see also McDonagh et al, 1998a).…”

Section: Provisional Classification Of Sc Cells Into Five Main Groupsmentioning

confidence: 88%

“…11A) and in vitro SC-muscle preparations (Currie and Lee, 1966;McDonagh et al, 1996b). Our prediction is that an MN with an intermediate f/I slope value will subsequently be shown to innervate nontwitch muscle fibers (McDonagh et al, 1998a;Stuart et al, 1998).…”

Section: Type Identification Of Turtle Spinal Insmentioning

confidence: 91%

“…The point of maximum increase in the rate of depolarization to produce the upstroke of the spike of this AP provided the V Rh value. The calculation of ⌬V Rh (V r Ϫ V m at spike onset) was limited to 69% of the MN ϩ IN-N sample in which bridge balance was assured between V r and spike onset (for review of this and related issues, see Gustafsson and Pinter, 1984;McDonagh et al, 1998a).…”

Section: Measurement Of Membrane Propertiesmentioning

confidence: 99%

“…minutes (range ϭ 43-54 minutes). During this time, numerous other tests of these cells were performed, including tests of R N and f/I slope and spike frequency adaptation (the latter two were repeated three times; preliminary results from repeated I-f tests and spike frequency adaptation studies have been reported elsewhere: Gilliam et al, 1995;Gorman et al, 1995a;McDonagh et al, 1998a). One of the five IN-S cells in particular demonstrated the robustness of the spike-generating mechanism in this preparation.…”

Section: Provisional Classification Of Sc Cells Into Five Main Groupsmentioning

confidence: 99%

“…R N , input resistance; I Rh , rheobase (threshold) current for one action potential; f/I slope, slope of the stimulus current-spike frequency relation; ϪN, nonspontaneous firing; ϪS, spontaneous firing. Analysis of spike frequency adaptation during 30 seconds of constant current stimulation McDonagh et al, 1998a) showed that most cells had not completely adapted by 2 seconds, the time at which the f/I slope was evaluated. Some cells demonstrated evidence of an underlying plateau potential (Hounsgaard and Kjaerulff, 1992), and their spike frequency increased transiently during the first 2 seconds of stimulation.…”

Section: I-f Relation For the Five Main Cell Groupsmentioning

confidence: 99%

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Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

et al. 1998

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The purpose of the present study was to compare, in motoneurons (MNs) vs. interneurons (INs), selected passive, transitional, and active (firing) properties, as recorded in slices of lumbosacral spinal cord (SC) taken from the adult turtle. The cells were provisionally classified on the basis of (1) the presence (in selected INs) or absence (MNs and other INs) of spontaneous discharge, (2) a cluster analysis of selected properties of the nonspontaneously firing cells, (3) a comparison to previous data on turtle MNs and INs, and (4) a qualitative comparison of the results with those reported for other vertebrate species (lamprey, cat). The provisional nomenclature accommodated properties appropriate for solely MNs (Main MN group) vs. nonspontaneously firing INs (Main IN-N) vs. spontaneously firing INs (IN-S) and for neurons with two degrees of intermediacy between the Main MN and the Main IN-N groups (Overlap MN, Overlap MN/IN). Morphological reconstructions of additional cells, which had been injected with biocytin during the electrophysiological tests, were shown to provide clear-cut support for the provisional classification procedure. The values for the measured parameters in the 96 tested cells covered the spectrum reported previously across adult vertebrate species and were robust in measurements made on different SC slices up to 5 days after their removal from the host animal. The interspecies comparisons permitted the predictions that (1) our Main MN and Overlap MN cells would be analogous to two MN types that innervate fast-twitch and slow-twitch skeletomotor muscle fibers, respectively, in the cat, and (2) the MNs in our Overlap MN/IN group probably innervate slow (nontwitch, tonic) muscle fibers whose presence has recently been established in the turtle hindlimb. In summary, the results bring out the utility of the SC slice preparation of the turtle for study of spinal motor mechanisms in adult tetrapod vertebrates, particularly as an adjunct to the in vivo cat, because of the ease with which robust measurements can be made of the active properties of both MNs and INs.

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“…Repeated testing of these cells appeared to have little effect on the steady-state firing rates for 10-30 seconds of stimulation ( Fig. 3E; see also McDonagh et al, 1998a).…”

Section: Provisional Classification Of Sc Cells Into Five Main Groupsmentioning

confidence: 88%

Section: Type Identification Of Turtle Spinal Insmentioning

confidence: 91%

Section: Measurement Of Membrane Propertiesmentioning

confidence: 99%

Section: Provisional Classification Of Sc Cells Into Five Main Groupsmentioning

confidence: 99%

Section: I-f Relation For the Five Main Cell Groupsmentioning

confidence: 99%

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Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

et al. 1998

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Associations between the morphology and physiology of ventral‐horn neurons in the adult turtle

McDonagh

Hornby

Reinking

et al. 2002

J of Comparative Neurology

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This study compared some morphologic and physiological properties of adult turtle spinal motoneurons (MNs) vs. interneurons (INs). Reconstructions were made of 20 biocytin-stained cells, which had been previously studied physiologically in 2-mm-thick slices of lumbosacral spinal cord. The intracellularly measured physiological properties included resting potential, input resistance (R(N)), threshold (rheobase, I(Rh)), and slope of the stimulus current (I) -spike frequency (f) relation. The seven morphologic properties that were quantified for each cell included three indices of somal size (diameter, area, volume), and four of dendritic size: the number of first- and last-order branches, rostrocaudal extent, and sigma individual lengths. Significant differences were shown between all seven morphologic parameters for MNs vs. INs. Despite the small sample size, significant differences were also shown for five of seven parameters for high-threshold vs. low-threshold MNs, and three of seven for low-threshold MNs vs. INs. These latter three parameters were the number of terminal dendritic branches, their rostrocaudal extent, and the sigma dendritic lengths. Linear associations for the MN + IN and the MN samples were stronger between the four dendritic parameters than between soma-dendritic ones. Exponential associations between morphologic and physiological properties were mostly significant (28 of 30), and their strength was in the order I(Rh) < R(N) < f/I slope for the MN +IN sample and I(Rh) < R(N) = f/I slope for the MN sample. There is discussion of the relevance of the above findings to the provisional classification of turtle ventral-horn neurons on the basis of electrophysiology alone.

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Immunohistochemical and hodological characterization of calbindin‐D28k‐containing neurons in the spinal cord of the turtle, Pseudemys scripta elegans

Morona

López

Domı́nguez

et al. 2007

Microscopy Res & Technique

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Neurons and fibers containing the calcium-binding protein calbindin-D28k (CB) were studied by immunohistochemical techniques in the spinal cord of adult and juvenile turtles, Pseudemys scripta elegans. Abundant cell bodies and fibers immunoreactive for CB were widely and distinctly distributed throughout the spinal cord. Most neurons and fibers were labeled in the superficial dorsal horn, but numerous cells were also located in the intermediate gray and ventral horn. In the dorsal horn, most CB-containing cells were located in close relation to the synaptic fields formed by primary afferents, which were not labeled for CB. Double immunohistofluorescence demonstrated distinct cell populations in the dorsal horn labeled only for CB or nitric oxide synthase, whereas in the dorsal part of the ventral horn colocalization of nitric oxide synthase was found in about 6% of the CB-immunoreactive cells in this region. Choline acetyltransferase immunohistochemistry revealed that only about 2% of the neurons in the dorsal part of the ventral horn colocalized CB, whereas motoneurons were not CB-immunoreactive. The involvement of CB-containing neurons in ascending spinal projections to the thalamus, tegmentum, and reticular formation was demonstrated combining the retrograde transport of dextran amines and immunohistochemistry. Similar experiments demonstrated supraspinal projections from CB-containing cells mainly located in the reticular formation but also in the thalamus and the vestibular nucleus. The revealed organization of the neurons and fibers containing CB in the spinal cord of the turtle shares distribution and developmental features, colocalization with other neuronal markers, and connectivity with other tetrapods and, in particular with mammals.

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Electrophysiological and morphological properties of neurons in the ventral horn of the turtle spinal cord

Cited by 16 publications

References 55 publications

Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

Associations between the morphology and physiology of ventral‐horn neurons in the adult turtle

Immunohistochemical and hodological characterization of calbindin‐D28k‐containing neurons in the spinal cord of the turtle, Pseudemys scripta elegans

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