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The selectivity of rostroventral medulla descending control of spinal sensory inputs shifts postnatally from A-fibre to C-fibre evoked activity.

Koch, SC; Fitzgerald, M; (2014) The selectivity of rostroventral medulla descending control of spinal sensory inputs shifts postnatally from A-fibre to C-fibre evoked activity. J Physiol , 592 (7) pp. 1535-1544. 10.1113/jphysiol.2013.267518. Green open access

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Abstract

Brainstem descending control is crucial in maintaining the balance of excitation and inhibition in spinal sensory networks. In the adult, descending inhibition of spinal dorsal horn circuits arising from the brainstem rostroventral medial medulla (RVM) is targeted to neurons with a strong nociceptive C-fibre input. Before the fourth postnatal week, the RVM exerts a net facilitation of spinal networks but it is not known if this is targeted to specific dorsal horn neuronal inputs. Since the maturation from descending facilitation to inhibition occurs only after C-fibre central synaptic maturation is complete, we hypothesised that RVM facilitation in young animals is targeted to A-fibre afferent inputs. To test this, the RVM was stimulated while recording dorsal horn neuronal activity in vivo under isoflurane anaesthesia at postnatal day (P) 21 and P40 (adult). Electrical thresholds for A- and C-fibre evoked activity, spike counts and wind-up characteristics at baseline and during RVM stimulation (10μA-100μA, I0 Hz) were compared. In adults, RVM stimulation selectively increased the threshold for C-fibre-evoked activity while at P21 it selectively decreased the threshold for A-fibre evoked activity and these effects were correlated to the wind-up characteristics of the neuron. Thus the postnatal shift in RVM control of dorsal horn circuits is not only directional but also modality specific, from facilitation of A-fibre input in the young animal to inhibition of nociceptive C-input in the adult, with additional contextual factors. Descending control of spinal sensory networks serves very different functions in young and adult animals.

Type: Article
Title: The selectivity of rostroventral medulla descending control of spinal sensory inputs shifts postnatally from A-fibre to C-fibre evoked activity.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1113/jphysiol.2013.267518
Publisher version: http://dx.doi.org/10.1113/jphysiol.2013.267518
Additional information: © 2014 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Keywords: Brainstem, Dorsal horn, Pain
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: https://discovery.ucl.ac.uk/id/eprint/1430147
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