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Pharmacological properties of a C‐fibre response evoked by saphenous nerve stimulation in an isolated spinal cord‐nerve preparation of the newborn rat
Author(s) -
Nussbaumer JeanClaude,
Yanagisawa Mitsuhiko,
Otsuka Masanori
Publication year - 1989
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1989.tb12607.x
Subject(s) - saphenous nerve , stimulation , spinal cord , compound muscle action potential , chemistry , spinal nerve , substance p , anatomy , depolarization , anesthesia , medicine , endocrinology , electrophysiology , neuropeptide , dorsum , receptor , psychiatry
1 An isolated spinal cord‐peripheral nerve preparation of the newborn rat was developed. In this preparation it is possible to record spinal reflexes from a lumbar ventral root in response to stimulation of the ipsilateral saphenous or obturator nerve. 2 Single shock, weak intensity stimulation of the saphenous nerve induced a fast conducted compound action potential in the L3 dorsal root and a fast depolarizing response in the ipsilateral L3 ventral root. As a stronger stimulus was applied to the saphenous nerve, a slowly conducted compound action potential appeared in the dorsal root and a slow depolarizing ventral root potential (v.r.p.) in the L3 ventral root. 3 Single shock stimulation of the obturator nerve induced a rapidly conducted compound action potential in the L3 dorsal root and monosynaptic and polysynaptic reflexes, with a fast time course, in the ipsilateral L3 ventral root. 4 The slow v.r.p. evoked by saphenous nerve stimulation was depressed by the tachykinin antagonist, [D‐Arg 1 , D‐Trp 7,9 , Leu 11 ] substance P (spantide), 4–16 μ m . The response recovered its original shape and size 30–60 min after the removal of this antagonist. 5 The saphenous nerve‐evoked slow v.r.p. was depressed by [Met 5 ] enkephalin (0.1–1 μ m ), dynorphin (1–13)(0.2 μ m ) and morphine (1–2 μ m ), and these effects were reversed by naloxone (1 μ m ). 6 Two endogenous peptides, galanin (1–2 μ m ) and somatostatin (1–2.5 μ m ), inhibited the slow v.r.p. evoked by saphenous nerve stimulation, whereas another endogenous peptide, calcitonin gene‐related peptide (0.1‐0.5 μ m ), potentiated the slow v.r.p. The slow v.r.p. was also inhibited by γ ‐ aminobutyric acid (GABA, 20 μ m ) and muscimol (0.2 μ m ), and their effects were antagonized by bicuculline (1 μ m ). 7 The present results suggest that substance P and neurokinin A are involved in the saphenous nerve‐evoked C‐fibre response in the spinal cord of the newborn rat.