2430237

Pharmacological properties of a C-fibre response evoked by saphenous nerve stimulation in an isolated spinal cord-nerve preparation of the newborn rat.

Article date: 1989/10/1

PubMed ID: 2430237

Journal name: British journal of pharmacology (ISSN: 0007-1188)

ABSTRACT

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-Arg1, D-Trp7,9, Leu11] substance P (spantide), 4-16 microM. 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 [Met5] enkephalin (0.1-1 microM), dynorphin (1-13)(0.2 microM) and morphine (1-2 microM), and these effects were reversed by naloxone (1 microM). 6. Two endogenous peptides, galanin (1-2 microM) and somatostatin (1-2.5 microM), inhibited the slow v.r.p. evoked by saphenous nerve stimulation, whereas another endogenous peptide, calcitonin gene-related peptide (0.1-0.5 microM), potentiated the slow v.r.p. The slow v.r.p. was also inhibited by gamma-aminobutyric acid (GABA, 20 microM) and muscimol (0.2 microM), and their effects were antagonized by bicuculline (1 microM). 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.

Author List: Nussbaumer J C, Yanagisawa M, Otsuka M

Publication Types: Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Narcotics; Peptides; Substance P; Naloxone; Somatostatin; gamma-Aminobutyric Acid; Galanin; spantide;

Mesh terms: Animals; Animals, Newborn/physiology; Electric Stimulation; Evoked Potentials/drug effects; Galanin; Naloxone/pharmacology; Narcotics/pharmacology; Nerve Fibers/drug effects; Peptides/pharmacology; Rats; Rats, Inbred Strains; Reflex, Monosynaptic/drug effects; Somatostatin/pharmacology; Spinal Cord/cytology; Substance P/analogs & derivatives; gamma-Aminobutyric Acid/pharmacology;

Citations: - 2417156

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