The burst-like firing of spinal neurons in rats with peripheral inflammation is reduced by an antagonist of N-methyl-D-aspartate

B. D. Grubb, R. C. Riley, P. J. Hope, L. Pubols, A. W. Duggan (Lead / Corresponding author)

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    16 Citations (Scopus)

    Abstract

    Ankle inflammation was induced in rats by subcutaneous injection of complete Freund's adjuvant and the firing properties of spinal neurons receiving afferent input from the inflamed areas were studied four to six days later. Comparable neurons in normal rats were also studied. In normal animals the response of neurons to ankle compression consisted of a brief burst of action potentials followed by sustained firing during stimulus application. On cessation of the stimulus there was no prolonged after discharge. In rats with an inflamed ankle, compression of the ankle produced firing while the stimulus was applied, but with 17 of 22 neurons there was a prolonged (219 ± 55 s) post-stimulus afterdischarge. All neurons studied in rats with peripheral inflammation fired with intermittent bursts of action potentials, particularly during the afterdischarge and spontaneous firing. The N-methyl-D-aspartate receptor antagonist DL-2-amino-5-phosphonopentanoate was ejected microiontophoretically near the cells studied. The major effect was a near abolition of bursts present in spontaneous firing and post-stimulus afterdischarges with a lesser reduction in firing during stimulus application. Effects on afterdischarge duration were variable. Since firing in bursts is known to increase transmitter release at some sites in the brain, it is proposed that when the relevant spinal neurons fire in bursts, additional intraspinal pathways are recruited and this contributes to the expanded receptive fields of neurons and possibly to the enhanced pain experienced by manipulation of inflamed peripheral tissues.

    Original languageEnglish
    Pages (from-to)1077-1086
    Number of pages10
    JournalNeuroscience
    Volume74
    Issue number4
    DOIs
    Publication statusPublished - Oct 1996

    Keywords

    • Afterdischarges
    • Bursts
    • NMDA receptors
    • Peripheral inflammation
    • Spinal neurons

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