The neuropeptide FF analogue, 1DMe, acts as a functional opioid autoreceptor antagonist in the rat spinal cord

doi:10.1016/S0014-2999(01)01384-X

European Journal of Pharmacology

Volume 430, Issues 2–3, 2 November 2001, Pages 273-276

https://doi.org/10.1016/S0014-2999(01)01384-X Get rights and content

Abstract

We assessed the possible influence of a neuropeptide FF analogue, 1DMe ([d-Tyr¹,(NMe)Phe³]neuropeptide FF), on the inhibitory action of endogenous and exogenous ∂-opioid receptor agonists on K⁺-evoked [Met⁵]-enkephalin release from superfused rat spinal cord slices. 1DMe (0.1–10 μM) dose-dependently enhanced the increase in superfusate [Met⁵]-enkephalin content due to the peptidase inhibitors thiorphan (1 μM) and bestatin (20 μM), and prevented the reduction in [Met⁵]-enkephalin release due to stimulation of ∂ receptors by 1 μM deltorphin I. Because it had the same effects as ∂-opioid receptor antagonists, 1DMe might act through the functional blockade of presynaptically located ∂-opioid autoreceptors.

Introduction

In rodents, neuropeptide FF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH₂) can exert either anti-opioid or opioid-like effects when it is injected intracerebroventricularly or intrathecally (i.t.), respectively (Roumy and Zajac, 1998). Thus, through the latter route of injection, neuropeptide FF as well as 1DMe ([d-Tyr¹,(NMe)Phe³]neuropeptide FF), a high affinity analogue partially protected from enzymatic breakdown (Gicquel et al., 1992), mimic the antinociceptive action of opioids in rats. Although neuropeptide FF and its analogues do not bind to opioid receptors, their antinociceptive action can be markedly reduced by opioid receptor antagonists (Roumy and Zajac, 1998). Indeed, 1DMe-induced antinociception very likely occurs through an induced release of [Met⁵]-enkephalin within the spinal cord (Ballet et al., 1999).

Mechanisms underlying the stimulatory effect of 1DMe on [Met⁵]-enkephalin release remain to be determined. Two-thirds of the terminals showing [Met⁵]-enkephalin-like immunoreactivity in the superficial layers of the spinal cord are endowed with ∂-opioid receptor-like immunoreactivity (Cheng et al., 1995). [Met⁵]-enkephalin very likely reduces its own release by acting at these receptors, whose blockade, as expected, leads to an enhanced release of [Met⁵]-enkephalin (Cesselin et al., 1999). Neuropeptide FF-induced inhibition of synaptic transmission could be attributable to a reduced probability of presynaptic release rather than to a depression of postsynaptic sensitivity (Chen et al., 2000). The aim of the present study was to directly assess the hypothesis that stimulation of spinal neuropeptide FF receptors could modulate [Met⁵]-enkephalin release under the control of presynaptically located opioid receptors.

Section snippets

Materials and methods

Male Sprague–Dawley rats (Centre d'élevage R. Janvier, Le Genest-Saint Isle, France) of 280–340 g body weight were kept under controlled environmental conditions (22 °C, 12 h alternate light–dark cycles, 60% humidity, food and water ad libitum) for at least 1 week before being used for the experiments.

All the procedures involving animals and their care were conducted in conformity with the institutional guidelines that are in compliance with national and international laws and policies (Council

Results

The outflow of [Met⁵]-enkephalin-like material remained essentially stable under control conditions ([K⁺]=5.4 mM) during the whole collection period. K⁺-induced depolarisation enhanced [Met⁵]-enkephalin-like material release, and the K2/K1 ratio, remarkably constant from one perfusion chamber to another, was close to 0.25 (see Fig. 1, Fig. 2).

Under control conditions, except thiorphan plus bestatin, none of the drugs presently tested affected the spontaneous outflow of [Met⁵]-enkephalin-like

Discussion

Although previous investigations indicated that 1DMe, when applied i.t., dose-dependently increased the release of [Met⁵]-enkephalin-like material from the spinal cord of anaesthetised rats (Ballet et al., 1999), this compound was presently found to exert no effect on the spontaneous outflow of the peptide from spinal cord slices. In fact, this result is not surprising since the spontaneous [Met⁵]-enkephalin-like material outflow in vitro was shown to be only partly dependent on extracellular Ca

Acknowledgements

This research was supported by grants from INSERM.

References (9)

S. Ballet et al.
The neuropeptide FF analogue, 1DME, enhances in vivo met-enkephalin release from the rat spinal cord
Neuropharmacology
(1999)
S. Gicquel et al.
Analogues of F8Famide resistant to degradation, with high affinity and in vivo effects
Eur. J. Pharmacol.
(1992)
M. Roumy et al.
Neuropeptide FF, pain and analgesia
Eur. J. Pharmacol.
(1998)
F. Cesselin et al.
Basic and regulatory mechanisms of in vitro release of met-enkephalin from the dorsal zone of the spinal cord
J. Neurochem.
(1984)

There are more references available in the full text version of this article.

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Neuropeptide FF (NPFF) modulates the opioid system by exerting functional anti-opioid activity on neurons, the mechanism of which is unknown. By using a model of SH-SY5Y cells, we recently postulated that anti-opioid activity likely takes place upstream from the signaling cascade, suggesting that NPFF receptors could block opioid receptors by physical interaction. In the present study, fluorescence techniques were used to monitor the physical association and the dynamic of NPFF₂ and μ-opioid (MOP) receptors tagged with variants of the green fluorescent protein. Importantly, cyan fluorescent protein-tagged NPFF₂ receptors retained their capacity to antagonize opioid receptors. Fluorescence resonance energy transfer (FRET) and coimmunoprecipitation studies indicate that NPFF and MOP receptors are close enough to generate a basal FRET signal. The opioid agonist Tyr-d-Ala-Gly-NMe-Phe-Gly-ol disrupts by 20-30% this FRET signal, mainly because it concomitantly induces 40% internalization of receptors. In contrast, the NPFF analog 1DMe significantly increases by 10-15% the basal FRET signal, suggesting an association between both receptors. In addition, 1DMe reduces, by half, MOP receptor internalization, indicating that, besides a functional blockade of opioid receptors, the NPFF analog also inhibits their internalization. Finally, as a first report showing the modulation of the mobility of a G-protein-coupled receptor by another one, fluorescence recovery after photobleaching analysis reveals that 1DMe modifies the lateral diffusion of MOP receptors in the cell membrane, changing them from a confined to a freely diffusing state. By promoting NPFF-MOP receptor heteromerization, 1DMe could disrupt the domain organization of MOP receptors in the membrane, resulting in a reduction of opioid response.
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Short communicationThe neuropeptide FF analogue, 1DMe, acts as a functional opioid autoreceptor antagonist in the rat spinal cord

Abstract

Introduction

Section snippets

Materials and methods

Results

Discussion

Acknowledgements

Neuropharmacology

Eur. J. Pharmacol.

Eur. J. Pharmacol.

Basic and regulatory mechanisms of in vitro release of met-enkephalin from the dorsal zone of the spinal cord

J. Neurochem.

Short communication
The neuropeptide FF analogue, 1DMe, acts as a functional opioid autoreceptor antagonist in the rat spinal cord