Elsevier

Neuroscience

Volume 74, Issue 1, September 1996, Pages 13-20
Neuroscience

METABOTROPIC GLUTAMATE RECEPTOR ACTIVATION CONTRIBUTES TO NOCICEPTIVE REFLEX ACTIVITY IN THE RAT SPINAL CORD IN VITRO

https://doi.org/10.1016/0306-4522(96)00101-7Get rights and content

Abstract

The contribution of metabotropic glutamate receptor activation to the spinal segmental reflex response evoked at high-intensity electrical stimulation, suggesting a role in nociception, has been examined in an in vitro preparation of neonatal rat spinal cord. Segmental reflex responses were recorded as a ventral root depolarization evoked following drug perfusion to the spinal cord or by electrical activation of high-threshold nociceptive afferent fibres. Superfusion of the selective metabotropic glutamate receptor agonist, (1 S3 R)-1-aminocyclopentane-1,3-dicarboxylic acid [(1 S,3 R)-ACPD], to the spinal cord produced a dose-dependent, reversible ventral root depolarization (ec50 = 58 ± 7 μM; n = 4), which was antagonized by the selective metabotropic glutamate receptor antagonist, (+)-α-methyl-4-carboxyphenylglycine (MCPG; ic50 = 243 ± 61 μM; n = 4). MCPG, over the same concentration range (10 μM-5.0 mM) did not affect N-methyl- d-aspartate-induced ventral root depolarizations. In contrast, the specific N-methyl- d-aspartate receptor antagonist d(−)-2-amino-5-phosphonopentanoic acid (d-AP5) reduced N-methyl- d-aspartate-evoked ventral root depolarization but did not affect the depolarization evoked by (1 S,3 R)-ACPD, thus indicating the specificity of the antagonists for these aggregate responses.

MCPG significantly reduced the prolonged phase of the single shock C-fibre-evoked ventral root depolarization (ic50 = 2.9 ± 0.2 mM; n = 3–5). Low frequency high intensity stimulation of the dorsal root evoked a wind-up response, the amplitude of which was attenuated by both d-AP5 and MCPG in a dose-dependent manner. The ventral root depolarization evoked by capsaicin application (1.0 μM, 30 s) was blocked by both MCPG (ic50 = 809 ± 35 μM; n = 4) and d-AP5 (ic50 = 143 ± 43 μM; n = 4). These data suggest that both d-AP5 and MCPG reduced C-fibre-induced ventral root responses.

In addition to N-methyl- d-aspartate receptor, metabotropic glutamate receptor activation appears to be involved in the generation of the segmental spinal reflex evoked by high-intensity stimulation in the neonatal rat spinal cord in vitro. Copyright © 1996 IBRO. Published by Elsevier Science Ltd.

Section snippets

EXPERIMENTAL PROCEDURES

Hemisected spinal cords were prepared as described previously 31, 34 from 10–14-day-old Sprague-Dawley rat pups (weight 24–26 g) born in-house. Following Enflurane anaesthesia, animals were killed by decapitation and spinal cords removed and placed into aerated (95% O2 and 5% CO2) and cooled artificial cerebrospinal fluid (ACSF in mM; 138 NaCl; 3.35 KCl; 21.0 NaHCO3; 0.58 NaH2PO4; 10.0 glucose; 1.16 MgCl2; 1.26 CaCl2; pH 7.4). Spinal cords were hemisected and transferred to a recording chamber

RESULTS

The selective mGluR agonist, (1 S,3 R)-ACPD, superfused to the spinal cord for 30 s, produced reproducible and dose-dependent ventral root depolarizations (ec50 = 58 ± 7 μM; n = 4; Fig. 1).

The potency of selective mGluR and ionotropic receptor antagonists was subsequently determined against concentrations of agonists which evoked submaximal ventral root responses [NMDA: 100 μM; [33] (1 S,3 R)-ACPD: 100 μM]. NMDA-induced ventral root responses were blocked by submaximal concentrations of d-AP5

DISCUSSION

In the present study we have examined the contribution of mGluR activation to the nociceptive segmental reflex in isolated spinal cords prepared from rat pups (10–14 days old), and compared the contribution of mGluR with NMDA receptor activation.

Ventral root responses measured after dorsal root stimulation are complex events which involve the release of neuropeptides and excitatory amino acids, and activation of postsynaptic receptors. [31] It has been determined previously that both ionotropic

CONCLUSION

In addition to d-AP5, MCPG is also effective in reducing C-fibre-induced ventral root responses, hence mGluR and NMDA receptor activation are involved in the generation of the segmental nociceptive reflex.

References (41)

Cited by (52)

  • NMDA receptor mediates chronic visceral pain induced by neonatal noxious somatic stimulation

    2015, European Journal of Pharmacology
    Citation Excerpt :

    Glutamate acts on two ionotropic receptor subtypes including NMDA (N-methyl-d-aspartate) and AMPA/kainite that are involved in plasticity, brain development, learning, excitatory synaptic transmission and long-term potentiation (Banerjee et al., 2009; Park et al., 2013; Yoshimura et al., 2003). The “Wind-up” of spinal neurons to somatic nociceptive stimuli and long-term potentiation due to synaptic plasticity is believed to be largely mediated by NMDARs (Boxall et al., 1996; Davies and Lodge, 1987; Dickenson and Sullivan, 1987; Randic et al., 1993; Liu and Sandkühler, 1995). The NMDAR is composed of 2 types of homologous membrane-spanning subunits, NR1 and NR2 (Gonda, 2012; Laube et al., 1997).

  • Glutamate potentiates lipopolysaccharide-stimulated interleukin-10 release from neonatal rat spinal cord astrocytes

    2012, Neuroscience
    Citation Excerpt :

    At 1 mM NaOH did not affect solution pH, and 0.1% DMSO did not affect LPS+glutamate-stimulated IL-10 release. All antagonists and agonists were used at concentrations that were within one order of magnitude above their EC50 or IC50 (Dragland-Meserve et al., 1985; Foster and Wong, 1987; Andreasen et al., 1989; Whittemore and Koerner, 1989; Manzoni et al., 1991; Sather et al., 1992; von Stebut et al., 1994; Wieprecht et al., 1994; Wyllie and Cull-Candy, 1994; Boxall et al., 1996; Schoepp et al., 1996; Davis et al., 1998; Seebeck et al., 1998; Brauner-Osborne et al., 1999; Vetter et al., 1999; De Colle et al., 2000; Noda et al., 2000; Shiraishi et al., 2001; Kato et al., 2005; Barker et al., 2006; Chiocchetti et al., 2006; Abe and Hiraki, 2009). Levels of IL-10 protein in the medium were quantified using a BD OptEIA Rat IL-10 ELISA Set (BD Biosciences, San Diego, CA, USA), with a minimum reliable detection level of 31.25 pg/ml.

  • Up-regulation of astrocyte metabotropic glutamate receptor 5 by amyloid-β peptide

    2009, Brain Research
    Citation Excerpt :

    Conversely, the expression of group I and II mGlu receptors by cultured astrocytes is dynamically controlled and is up-regulated by treatment with growth factors such as basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and transforming growth factor-α (TGFα) (Miller et al., 1995; Minoshima and Nakanishi, 1999, Aronica et al., 2003). In vivo studies have shown that changes in astrocyte expression of mGlu receptors occur in response to a variety of brain insults including nociception (Boxall et al., 1996), seizures, (Ulas et al., 2000; Ferraguti et al., 2001, Aronica et al., 2000, Tang et al., 2001) and neurodegeneration (Aronica et al., 2001). Up-regulation of mGlu5 has been described in the cerebral cortex of Down's syndrome and AD patient brains (Oka and Takashima, 1999) as well as in cases with multiple sclerosis (Geurts et al., 2003).

  • Spinal Cord Mechanisms of Hyperalgesia and Allodynia

    2008, The Senses: A Comprehensive Reference
View all citing articles on Scopus
1

Present address: Division of Physiology, UMDS, St. Thomas' Campus, Lambeth Palace Rd, London SE1 7EH, U.K.

View full text