Plateau‐generating neurones in the dorsal horn in an in vitro preparation of the turtle spinal cord.

Russo, Raúl E.; Hounsgaard, Jørn

doi:10.1113/jphysiol.1996.sp021363

Cited by 104 publications

(125 citation statements)

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“…These impedances are substantially higher than those reported for trochlear neurons in other species but are within the range of values reported for spinal motoneurons in the turtle (Russo and Hounsgaard 1996). SPIKE AHP.…”

Section: Intrinsic Membrane Propertiesmentioning

confidence: 41%

Morphology, Intrinsic Membrane Properties, and Rotation-Evoked Responses of Trochlear Motoneurons in the Turtle

Jones¹,

Ariel²

2008

Journal of Neurophysiology

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Jones MS, Ariel M. Morphology, intrinsic membrane properties, and rotation-evoked responses of trochlear motoneurons in the turtle. J Neurophysiol 99: 1187-1200, 2008. First published December 26, 2007 doi:10.1152/jn.01205.2007. Intrinsic properties and rotationevoked responses of trochlear motoneurons were investigated in the turtle using an in vitro preparation consisting of the brain stem with attached temporal bones that retain functional semicircular canals. Motoneurons were divided into two classes based on intrinsic properties. The first class exhibited higher impedance (123.0 Ϯ 11.0 M⍀), wider spikes (0.99 Ϯ 0.05 ms), a single spike afterhyperpolarization (AHP), little or no spike frequency adaptation (SFA), and anomalous rectification, characterized by an initial "sag" in membrane potential in response to hyperpolarizing current injection. The second class exhibited lower impedance (21.8 Ϯ 2.5 M⍀), narrower spikes (0.74 Ϯ 0.03 ms), a double AHP, substantial SFA, and little or no rectification. Vestibular responses were evoked by horizontal sinusoidal rotation (1/12-1/3 Hz; peak velocity: 30 -100°/s). Spiking in higher-impedance cells was recruited earlier in the response and exhibited a more limited dynamic range relative to that of lower impedance cells. Spiking evoked by injecting depolarizing current during rotation was blocked during contraversive motion and was consistent with a shunting inhibition. No morphological features were identified in neurobiotinfilled cells that correlated with the two physiological classes. Recovered motoneurons were multipolar but exhibited a less-complex dendritic morphology than ocular motoneurons of similarly sized mammals. The two physiologically defined cell classes have homologues in other vertebrates, suggesting that intrinsic membrane properties play an important role in oculomotor processing. I N T R O D U C T I O NMotoneurons in the oculomotor, trochlear, and abducens nuclei comprise the common final output pathway for the control of eye movement. A variety of descending and brain stem projections converge on these motoneurons (ButtnerEnnever and Horn 1997), which transform a complex spatiotemporal pattern of synaptic input into a rate-coded spike train that drives the extraocular muscles in a coordinated and precise fashion. These neurons are not only responsible for the generation of voluntary eye movements but also participate in critical brain stem reflexes such as the vestibuloocular reflex (VOR), a compensatory movement of the eyes during motion of the head that acts to stabilize the visual scene on the retina (Wilson and Melvill-Jones 1976).There has been intensive study of oculomotor physiology and the VOR over the last few decades, motivated not only by its clinical relevance but also the utility of the system as a model of neural control (Schwarz 1976;Young 1995). One issue that remains poorly understood is the role of intrinsic membrane properties in shaping motoneuron output. In the spinal cord, the role of intrinsic properties in influencing syna...

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Section: Intrinsic Membrane Propertiesmentioning

confidence: 41%

Morphology, Intrinsic Membrane Properties, and Rotation-Evoked Responses of Trochlear Motoneurons in the Turtle

Jones¹,

Ariel²

2008

Journal of Neurophysiology

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“…The soma locations of flexion cells were similar to those of sensory interneurons activated by limb skin stimulation (Schouenborg et al, 1995) and wide dynamic range neurons (Craig, 2003;You et al, 2003;Sandrini et al, 2005) in mammalian dorsal horn and overlapped with those of burst-generating neurons (Russo and Hounsgaard, 1996b), plateau-generating neurons (Russo and Hounsgaard, 1996a), and neurons showing windup (Russo and Hounsgaard, 1994) in turtle dorsal horn. Dorsolateral commissural interneurons in embryonic tadpoles also have dorsal soma locations and mediate a disynaptic reflex in which stroking the trunk skin evokes contralateral axial muscle contraction (Li et al, 2003).…”

Section: Morphological Comparisons To Dorsal Horn Cells In Other Studiesmentioning

confidence: 63%

Spinal Interneurons That Are Selectively Activated during Fictive Flexion Reflex

Berkowitz¹

2007

J. Neurosci.

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Behavioral choices in invertebrates are mediated by a combination of shared and specialized circuitry, including neurons that are inhibited during competing behaviors. Less is known, however, about the neural mechanisms of behavioral choice in vertebrates. The spinal cord can appropriately select among several types of limb movements, including limb withdrawal (flexion reflex), scratching, and locomotion, and thus is conducive to examination of vertebrate mechanisms of behavioral choice. Flexion reflex can interrupt and reset the rhythm of scratching and locomotion, suggesting that a combination of shared and specialized circuitry contributes to these behaviors, but little is known about the interneurons involved. Here, I used in vivo intracellular recording and dye injection to identify a group of spinal interneurons that are strongly activated during fictive flexion reflex but inhibited during fictive scratching and fictive swimming. These flexion-selective interneurons are typically rhythmically hyperpolarized during fictive scratching and fictive swimming. This hyperpolarization can be maximal during the ipsilateral hip flexor bursts of rhythmic limb motor patterns, although these cells are strongly activated during the ipsilateral hip flexor bursts of fictive flexion reflex. Thus, these interneurons are relatively specialized for fictive limb withdrawal, rather than contributing to the hip flexor phase of multiple types of limb movements. These flexion-selective cells are physiologically and morphologically distinguishable from a recently described group of spinal interneurons (transverse interneurons) that are strongly activated during both fictive flexion reflex and fictive scratching. Thus, spinal interneurons with distinct behavioral roles may to some extent be morphologically distinguishable.

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“…In three motoneurons, a large (Յ30 mV), sudden depolarization occurred during the sustained firing (see Fig. 7E, right); a similar depolarization was found in cat MNs (Bennet et al 1998) as well as in dorsal horn neurons of the spinal cord of the turtle and of the rat (Morisset and Nagy 1998;Russo and Hounsgaard 1996). FIG. 6.…”

Section: Intracellular Recordingsmentioning

confidence: 87%

Sustained Firing of Alpha and Gamma Hind Limb Motoneurons Induced by Stimulation of the Pudendal Nerve

Cueva-Rolón

Delgado‐Lezama

Raya

et al. 2002

Journal of Neurophysiology

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oz-Martínez. Sustained firing of alpha and gamma hind limb motoneurons induced by stimulation of the pudendal nerve. J Neurophysiol 88: 3232-3242, 2002; 10.1152/jn.00157.2002. Axons from receptors in the cat vaginal wall run in the sensory pudendal nerve (SPN), and brief (Ͻ10 s) vaginal probing (VP) in the decerebrate cat produces a long-lasting (Ͼ1 min) contraction of the triceps surae (TS) muscles. The aim of the present project was to find out whether brief SPN stimulation also produces sustained TS response and, eventually, to study the mechanisms involved in it. Decerebrate female cats were used. In some cats, TS electromyography (EMG) and tension response were recorded; stimulation of left SPN with single or repetitive trains of shocks produced a bilateral TS response that outlasted the stimulus Ͼ1 min as VP did. In paralyzed cats (pancuronium; Panc), intracellular recordings were made from hind limb motoneurons (MNs). SPN stimulation produced a depolarization Յ5 s long and occasional cell firing only lasting Ͻ2.5 s; this is in contrast with the prolonged TS postdischarge seen in nonparalyzed cats. If MNs were depolarized below the firing threshold by current injection, about half of them showed bistable firing that could last several minutes in response to SPN train. It is suggested that MNs might hyperpolarize after Panc injection. Before Panc injection, SPN train produced long-lasting (Ͼ1 min) electroneurographic (ENG) postdischarge in a small filament of the medial gastrocnemius (MG) nerve; the MG EMG postdischarge was also recorded. Large spikes (LS) and small spikes (SS) were distinguished in the ENG. During the postdischarge, LS frequency and the integrated EMG activity correlated well (r Ͼ 0.9); no correlation was found between SS and EMG. After Panc injection, LS postdischarge was absent but the SS postdischarge remained. LS followed by EMG potential were also evoked by brief TS stretch (reflex LS); single shocks to SPN only elicited SS that were not followed by EMG potential. It is concluded that alpha axons and gamma axons produced LS and SS, respectively, and that SPN activates gamma axons. It is proposed that, in the nonparalyzed cats, the stimulation of SPN with trains of shocks might cause an increase in the afferent inflow from muscle spindles to alpha MNs through the sustained firing of gamma MNs. The increased excitatory inflow would depolarize alpha MNs and allow bistable MN firing; Panc would decrease this inflow by blocking transmission to the spindle fibers.

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Plateau‐generating neurones in the dorsal horn in an in vitro preparation of the turtle spinal cord.

Cited by 104 publications

References 34 publications

Morphology, Intrinsic Membrane Properties, and Rotation-Evoked Responses of Trochlear Motoneurons in the Turtle

Morphology, Intrinsic Membrane Properties, and Rotation-Evoked Responses of Trochlear Motoneurons in the Turtle

Spinal Interneurons That Are Selectively Activated during Fictive Flexion Reflex

Sustained Firing of Alpha and Gamma Hind Limb Motoneurons Induced by Stimulation of the Pudendal Nerve

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