ANALYSIS OF THE EFFECTS OF <i>p</i>‐METHOXY‐PHENYLETHYLAMINE ON SPINAL CORD NEURONES

Jordan, Larry M.; McCrea, David A.

doi:10.1111/j.1476-5381.1976.tb07467.x

Cited by 16 publications

(5 citation statements)

References 19 publications

(30 reference statements)

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“…An immunohistochemical study found on average, 4 serotonergic boutons on cat Renshaw cells (Carr et al 1999), confirming earlier reports that unlike for motoneurons, serotonin has a weak effect on Renshaw cells. Moreover, serotonin acts to inhibit Renshaw cells (Jordan and McCrea 1976). At present, voltage-gated channels have not been identified on the dendrites of Renshaw cells.…”

Section: Physiological Implicationsmentioning

confidence: 86%

Comparison of the Morphological and Electrotonic Properties of Renshaw Cells, Ia Inhibitory Interneurons, and Motoneurons in the Cat

Bui

Cushing

Dewey

et al. 2003

Journal of Neurophysiology

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. The morphological and electrotonic properties of 4 motoneurons, 8 Ia inhibitory interneurons, and 4 Renshaw cells were compared. The morphological analysis, based on 3-D reconstructions of the cells, revealed that dendrites of motoneurons are longer and more extensively branched. Renshaw cells have dendrites that are shorter and simpler in structure. Dendrites of Ia inhibitory interneurons could be as long as those of motoneurons but the branching structure resembled that of Renshaw cells. Compartmental models were used to determine the electrotonic properties of the paths from each dendritic terminal to the soma. The attenuations of steady-state voltage changes in motoneurons were 3 and 7 times larger than in Ia inhibitory interneurons and Renshaw cells, respectively. The same relative order was observed for current attenuation and electrotonic length. The dendritic input resistances in Renshaw cells were 2 and 4 times larger than in Ia inhibitory interneurons and motoneurons, respectively. The difference in these electrotonic properties increased during higher synaptic activity as modeled by a decrease of R m . The peak amplitudes of voltage transients at sites of brief, synaptic-like changes in conductance were highly dependent on cell class and were largest in Renshaw cells and smallest in motoneurons. In combination with class-specific differences in the attenuation of transient voltage signals, this led to large differences in the peak amplitudes of somatic voltage transients. Differences in the rise times and half-widths of the voltage transients were observed as well. Thus, based on passive properties, each cell class has a unique set of input/output properties.

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Section: Physiological Implicationsmentioning

confidence: 86%

Comparison of the Morphological and Electrotonic Properties of Renshaw Cells, Ia Inhibitory Interneurons, and Motoneurons in the Cat

Bui

Cushing

Dewey

et al. 2003

Journal of Neurophysiology

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“…For instance, aberrant sprouting of primary afferents or expansion of interneuronal receptive and projective fields after SCI may augment the excitatory drive to spinal networks [ 134 ]. On the other hand, inhibition is affected by the interruption of serotoninergic descending tracts, which modulate inhibitory interneurons, like Renshaw cells [ 135 , 136 ]. Moreover, Renshaw cell recurrent circuitry might become disconnected from motoneurons [ 137 ] suppressing their excitatory drive to Renshaw cells, in turn reducing the GABAergic inhibitory feedback.…”

Section: Fast Synaptic Gabaergic Transmission Is Early Affected By Spinal Cord Injurymentioning

confidence: 99%

GABAergic Mechanisms Can Redress the Tilted Balance between Excitation and Inhibition in Damaged Spinal Networks

et al. 2021

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Correct operation of neuronal networks depends on the interplay between synaptic excitation and inhibition processes leading to a dynamic state termed balanced network. In the spinal cord, balanced network activity is fundamental for the expression of locomotor patterns necessary for rhythmic activation of limb extensor and flexor muscles. After spinal cord lesion, paralysis ensues often followed by spasticity. These conditions imply that, below the damaged site, the state of balanced networks has been disrupted and that restoration might be attempted by modulating the excitability of sublesional spinal neurons. Because of the widespread expression of inhibitory GABAergic neurons in the spinal cord, their role in the early and late phases of spinal cord injury deserves full attention. Thus, an early surge in extracellular GABA might be involved in the onset of spinal shock while a relative deficit of GABAergic mechanisms may be a contributor to spasticity. We discuss the role of GABA A receptors at synaptic and extrasynaptic level to modulate network excitability and to offer a pharmacological target for symptom control. In particular, it is proposed that activation of GABA A receptors with synthetic GABA agonists may downregulate motoneuron hyperexcitability (due to enhanced persistent ionic currents) and, therefore, diminish spasticity. This approach might constitute a complementary strategy to regulate network excitability after injury so that reconstruction of damaged spinal networks with new materials or cell transplants might proceed more successfully.

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“…Modulatory effects of monoamines on transmission between primary afferents and neurons in the mammalian spinal cord have been demonstrated for several neuronal populations, including various types of ascending tract neurons (Jordan et al, 1978, 1979); (Fleetwood‐Walker et al, 1985; Carlton et al, 1991; Jankowska et al, 1997a; Hammar et al, 2001) and interneurons, e.g. (Engberg and Ryall, 1965, 1966; Jordan and McCrea, 1976; Todd and Millar, 1983; Bras et al, 1989; Jankowska et al, 2000). Modulation of responses of individual functionally identified neurons of different populations by locally applied monoamines turned out to be highly differentiated, although the modulatory effects on neurons within a population have been relatively consistent.…”

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confidence: 99%

Serotoninergic and noradrenergic axons make contacts with neurons of the ventral spinocerebellar tract in the cat

Hammar

Maxwell

2002

J of Comparative Neurology

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Contacts between monoaminergic fibers and electrophysiologically identified neurons of the ventral spinocerebellar tract were investigated in the cat. Five neurons were labeled intracellularly with rhodamine dextran, and monoaminergic fibers were revealed with antibodies against serotonin and dopamine beta-hydroxylase. The distribution of appositions between monoaminergic varicosities and the soma and the whole length of dendrites of these neurons was examined by using a three-channel confocal microscope. The analysis showed that close appositions between monoaminergic fibers and labeled processes occurred over the whole surface of the neurons. The highest percentage of such appositions was found on proximal dendrites, for both serotonin (37%) and noradrenaline (57%). The total number of serotoninergic contacts (66-134 per neuron) by far exceeded that of noradrenergic contacts (3-36 per neuron). Contacts between serotoninergic fibers and two neurons were analyzed by using electron microscopy. These neurons were labeled intracellularly with horseradish peroxidase, and serotoninergic varicosities were identified by immunocytochemistry. Six of 10 serially analyzed boutons in apposition to proximal dendrites were found to form morphologic synapses. The identification of the remaining four was inconclusive. These results indicate that many of the appositions seen in confocal microscopy may represent direct synaptic contacts. They also indicate that monoaminergic neurons may modulate activity of neurons of the ventral spinocerebellar tract by direct postsynaptic actions in addition to any effects evoked by means of volume transmission.

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ANALYSIS OF THE EFFECTS OF p‐METHOXY‐PHENYLETHYLAMINE ON SPINAL CORD NEURONES

Cited by 16 publications

References 19 publications

Comparison of the Morphological and Electrotonic Properties of Renshaw Cells, Ia Inhibitory Interneurons, and Motoneurons in the Cat

Comparison of the Morphological and Electrotonic Properties of Renshaw Cells, Ia Inhibitory Interneurons, and Motoneurons in the Cat

GABAergic Mechanisms Can Redress the Tilted Balance between Excitation and Inhibition in Damaged Spinal Networks

Serotoninergic and noradrenergic axons make contacts with neurons of the ventral spinocerebellar tract in the cat

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