Long-term depression of C-fibre-evoked spinal field potentials by stimulation of primary afferent A delta-fibres in the adult rat.
Long-term potentiation (LTP) of spinal C-fibre-evoked field potentials can be induced by brief electrical stimulation of afferent C-fibres, by natural noxious stimulation of skin or by acute nerve injury. Here, we report that in urethane anaesthetized, adult rats prolonged high frequency burst stimulation of the sciatic nerve at Adelta-fibre strength produced long-term depression (LTD) of C-fibre-evoked field potentials, and also depressed the increased amplitudes of C-fibre-evoked field potentials recorded after LTP had been established (depotentiation). Electrical stimulation of Abeta-fibres failed to induce LTD or depotentiation. In spinalized rats, prolonged Adelta-fibre conditioning stimulation induced LTP rather than LTD of C-fibre-evoked field potentials. Thus, tonic descending inhibition may determine the direction of plastic changes in C-fibre-mediated synaptic transmission. Spinal application of the N-methyl-D-aspartic acid receptor antagonist D-APV blocked induction of LTD in intact rats and LTP in spinalized rats. The presently described LTD and the depotentiation of established LTP of C-fibre-evoked field potentials in spinal dorsal horn may underlie some forms of prolonged analgesia induced by peripheral nerve stimulation procedures.
Liu
X G
XG
II. Physiologisches Institut, Universität Heidelberg, Germany.
Morton
C R
CR
Azkue
J J
JJ
Zimmermann
M
M
Sandkühler
J
J
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate