Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Jan 1:2:76-83.
doi: 10.2174/1876386300902010076.

Microinjection of IL-1β into the trigeminal transition zone produces bilateral NMDA receptor-dependent orofacial hyperalgesia involving descending circuitry

Affiliations

Microinjection of IL-1β into the trigeminal transition zone produces bilateral NMDA receptor-dependent orofacial hyperalgesia involving descending circuitry

K Shimizu et al. Open Pain J. .

Abstract

Our recent studies indicate that the prototypic proinflammatory cytokine IL-1β is upregulated in astroglial cells in the trigeminal interplolaris/caudalis (Vi/Vc) transition zone, a region of the spinal trigeminal complex involved in trigeminal pain processing, after masseter muscle inflammation. Here we investigated the effect of microinjection of IL-1β into the Vi/Vc transition zone on orofacial nociception. The mechanical sensitivity of the orofacial site was assessed with von Frey microfilaments. The EF(50) values, defined as the von Frey filament force (g) that produces a 50% response frequency, were derived and used as a measure of mechanical sensitivity. A significant reduction in EF(50) indicates the occurrence of mechanical hyperalgesia/allodynia. Unilateral intra-Vi/Vc IL-1β (0.016-160 fmol) produced hyperalgesia/allodynia dose-dependently, which appeared at bilateral facial sites. The hyperalgesia was detectable as early as 30 min and lasted for 2-6 h (n=6, p<0.01). Intra-Vi/Vc pretreatment with an IL-1receptor antagonist (1 nmol) attenuated the IL-1β-induced hyperalgesia (p<0.01). Pre-injection of AP-5 (10 pmol) and MK-801 (20 pmol), two NMDA receptor antagonists, significantly attenuated IL-1β-induced hyperalgesia (p<0.05). Pretreatment with glial inhibitors fluorocitrate (120 pmol), minocycline (200 pmol) and propentofylline (10 pmol) did not attenuate IL-1β-induced hyperalgesia. Excitotoxic lesions of the rostral ventromedial medulla with ibotenic acid (2 μg) abolished IL-1β-induced contralateral hyperalgesia, suggesting a contribution of descending facilitatory drive. These results suggest that the IL-1β-produced effect on nociception was downstream to glial activation and involves interaction with NMDA receptors.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Mechanical hyperalgesia/allodynia induced by injection of IL-1β into the Vi/Vc transition zone of the rat. A. An example of caudal brain stem section stained with cresyl violet for histological verification of the site of microinjection. Arrow indicates the injection site in ventral Vi/Vc. Scale bar = 500 μm. cc, central canal; Py, pyramidal tract; sp5, spinal trigeminal tract; Vi/Vc, trigeminal subnuclei interpolaris/caudalis transition zone. B. Stimulus-response function curves illustrating the intensity-dependent head withdrawal responses to mechanical stimuli. Each curve was established with a series of subthreshold to suprathreshold range of von Frey filament forces and the response frequency is plotted against the stimulus intensity. IL-1β (160 fmol) was injected into the ventral Vi/Vc. The skin site above the masseter muscle was probed. Note that there was a leftward shift of the curve at 30 min after IL-1β injection compared to the pre-IL-1β curve (p<0.01), suggesting the development of mechanical hyperalgesia and allodynia. Best-fit curves were generated by nonlinear regression analysis (GraphPad Prism). C, D. The EF50s were derived from the respective stimulus-response frequency function curves and are plotted against time. Note significant decreases in EF50s at 30 min-6h after IL-1β injection, indicating IL-1β̃ induced bilateral hyperalgesia/allodynia. +, #: p<0.05; **, ++, ##: p<0.01 (ANOVA with repeated measures and post-hoc test). Dashed lines indicate interruption of the linearity of the time scale.
Figure 2
Figure 2
The effect of receptor antagonists on IL-1β̃ induced hyperalgesia. IL-1β (160 fmol) was injected into the ventral Vi/Vc. IL-1ra (A, 1 nmol), AP-5 (B, 10 pmol) and MK-801 (C, 20 pmol) was injected into the ventral Vi/Vc at 10 min prior to IL-1β injection. Pretreatment with IL-1ra, AP-5 and MK-801 prevented or attenuated IL-1β-induced hyperalgesia as compared to saline-pretreated rats. *, +, #: p<0.05; **, ++, ##: p<0.01 (ANOVA with repeated measures and post-hoc test).
Figure 3
Figure 3
The effect of glial inhibitors on IL-1β-induced orofacial hyperalgesia. IL-1β (160 fmol) was injected into the ventral Vi/Vc. Fluorocitrate (A) (FC, 120 pmol), minocycline (B) (MC, 200 pmol), and propentofylline (C) (PPF, 10 pmol) was injected into the ventral Vi/Vc at 10 min prior to IL-1β injection. Pretreatment with fluorocitrate, minocycline and propentofylline did not prevent IL-1β-induced hyperalgesia. *, +: p<0.05; **, ++: p<0.01 (ANOVA with repeated measures and post-hoc test).
Figure 4
Figure 4
Intra-RVM ibotenic acid (IBO) attenuated IL-1β-induced contralateral hyperalgesia. Ten-min before a unilateral injection of IL-1β into the Vi/Vc transition zone, IBO (2 μg/0.2 μl, n=5) was microinjected into the RVM to produce excitotoxic neuronal lesions in RVM. Saline was injected as a vehicle control. A. Schematic illustration of the microinjection sites and IBO-produced lesions. The extent of IBO-produced lesions is shown as dashed enclosures. The open circles indicate the injection sites for saline. B. Compared to saline-injected rats, RVM excitotoxic lesions prevented the development of contralateral hyperalgesia after injection of IL-1β into the Vi/Vc transition zone. C. Compared to saline control, there was a slight further decrease in EF50s on the ipsilateral site in the IBO-treated rats. ##, p<0.01, ###, p<0.001, saline vs. IBO (ANOVA with repeated measures and post-hoc test).

Similar articles

Cited by

References

    1. Watkins LR, Maier SF. Immune regulation of central nervous system functions: from sickness responses to pathological pain. J Intern Med. 2005;257:139–55. - PubMed
    1. Dinarello CA. Therapeutic strategies to reduce IL-1 activity in treating local and systemic inflammation. Curr Opin Pharmacol. 2004;4:378–85. - PubMed
    1. Kawasaki Y, Xu ZZ, Wang X, et al. Distinct roles of matrix metalloproteases in the early- and late-phase development of neuropathic pain. Nat Med. 2008;14:331–6. - PMC - PubMed
    1. Ren K, Torres R. Role of interleukin-1beta during pain and inflammation. Brain Res Rev. 2009;60:57–64. - PMC - PubMed
    1. Guo W, Wang H, Watanabe M, et al. Glial-cytokine-neuronal interactions underlying the mechanisms of persistent pain. J Neurosci. 2007;27:6006–18. - PMC - PubMed

LinkOut - more resources