Norepinephrine Facilitates Inhibitory Transmission in Substantia Gelatinosa of Adult Rat Spinal Cord (Part 2): Effects on Somatodendritic Sites of GABAergic Neurons |
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Authors: | Baba, Hiroshi M.D., Ph.D. Goldstein, Peter A. M.D. Okamoto, Manabu M.D., Ph.D. Kohno, Tatsuro M.D., Ph.D. Ataka, Toyofumi M.D.
Yoshimura, Megumu M.D., Ph.D Shimoji, Koki M.D., Ph.D.# |
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Affiliation: | Baba, Hiroshi M.D., Ph.D.*; Goldstein, Peter A. M.D.†; Okamoto, Manabu M.D., Ph.D.‡; Kohno, Tatsuro M.D., Ph.D.‡; Ataka, Toyofumi M.D.§; Yoshimura, Megumu M.D., Ph.D∥; Shimoji, Koki M.D., Ph.D.# |
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Abstract: | Background: It has been reported previously that norepinephrine, when applied to the spinal cord dorsal horn, excites a subpopulation of dorsal horn neurons, presumably inhibitory interneurons. In the current study, the authors tested whether norepinephrine could activate inhibitory interneurons, specifically those that are "GABAergic." Methods: A transverse slice was obtained from a segment of the lumbar spinal cord isolated from adult male Sprague-Dawley rats. Whole-cell patch-clamp recordings were made from substantia gelatinosa neurons using the blind patch-clamp technique. The effects of norepinephrine on spontaneous GABAergic inhibitory postsynaptic currents were studied. Results: In the majority of substantia gelatinosa neurons tested, norepinephrine (10-60 [mu]M) significantly increased both the frequency and the amplitude of GABAergic inhibitory postsynaptic currents. These increases were blocked by tetrodotoxin (1 [mu]M). The effects of norepinephrine were mimicked by the [alpha]1-receptor agonist phenylephrine (10-80 [mu]M) and inhibited by the [alpha]1-receptor antagonist WB-4101 (0.5 [mu]M). Primary-afferent-evoked polysynaptic excitatory postsynaptic potentials or excitatory postsynaptic currents in wide-dynamic-range neurons of the deep dorsal horn were also attenuated by phenylephrine (40 [mu]M). |
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