Effects of monoamines on interneurons in four spinal reflex pathways from group I and/or group II muscle afferents

@article{Jankowska2000EffectsOM,
  title={Effects of monoamines on interneurons in four spinal reflex pathways from group I and/or group II muscle afferents},
  author={Elzbieta Jankowska and Ingela Hammar and B. Chojnicka and Carina Hed{\'e}n},
  journal={European Journal of Neuroscience},
  year={2000},
  volume={12}
}
Effects of locally applied serotonin (5‐HT) and noradrenaline (NA) were tested on extracellularly recorded responses of single spinal interneurons in deeply anaesthetized cats. These effects were tested on: (i) interneurons mediating reciprocal inhibition from group Ia afferents; (ii) interneurons mediating non‐reciprocal inhibition from group Ia and Ib afferents; (iii) intermediate zone interneurons co‐excited by group I and II afferents; and (iv) dorsal horn interneurons excited by group II… 
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TLDR
The results of this study lead to the conclusion that strong presynaptic inhibition of transmission to intermediate zone interneurones allows a selective depression of disynaptic actions of group II muscle afferents on α‐ and γ‐motoneurones, mediated by these interneURones, and favours polysynapticactions of these afferentS.
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TLDR
The study indicates that intermediate zone interneurones may be activated by group II afferents both directly and via dorsal horn interneuranones and that synaptic actions of group II Afferents upon these interneuronones, and their subsequent actions upon motoneurones, may be modulated in parallel at the level of intermediate zone and dorsal horn.
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TLDR
The aim here is to reassess the basis for subdivision of adult mammalian spinal interneurons that mediate reflex actions from tendon organs and muscle spindle secondary endings into separate populations, and proposes renaming these neurons ‘group I/II interneeurons’.
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The morphological and electrophysiological data show that individual excitatory and inhibitory intermediate zone interneurons may operate in a highly differentiated way and thereby contribute to a variety of motor synergies.
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Findings provide a morphological basis for the modulatory actions of monoamines on premotor spinal interneurons in pathways from group II muscle afferents.
Both dorsal horn and lamina VIII interneurones contribute to crossed reflexes from feline group II muscle afferents
TLDR
It is concluded that dorsal horn interneurones contribute to the late actions of group II muscle afferents on contralateral motoneurones through their disynaptic actions on commissural interneURones.
Spinal interneurons that receive input from muscle afferents are differentially modulated by dorsolateral descending systems.
TLDR
Results suggest that a disruption of the descending system, such as occurs in spinal cord injury, will lead to a suppression of the interneuronal pathways with group Ia input while enhancing excitability within interneURonal pathways transmitting actions from higher threshold afferents.
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TLDR
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