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Serotonin Receptor 2A/C Is Involved in Electroacupuncture Inhibition of Pain in an Osteoarthritis Rat Model.

Li A, Zhang Y, Lao L, Xin J, Ren K, Berman BM, Zhang RX - Evid Based Complement Alternat Med (2011)

Bottom Line: Acupuncture can benefit patients with knee osteoarthritis by providing pain relief, improving joint function and serving as an effective complement to standard care.However, the underlying mechanisms of its effects are still not completely understood.The results showed that EA significantly decreases weight-bearing difference compared to sham EA.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrative Medicine, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.

ABSTRACT
Osteoarthritis currently has no cure. Acupuncture can benefit patients with knee osteoarthritis by providing pain relief, improving joint function and serving as an effective complement to standard care. However, the underlying mechanisms of its effects are still not completely understood. The present study, an investigation of the effectiveness and mechanisms of electroacupuncture (EA) in attenuating osteoarthritis pain in a rat model, is focused on the involvement of 5-hydroxytryptamine 2A/C (5-HT2A/C) receptors, which play an important role in pain modulation at the spinal level. Osteoarthritis was induced under isoflurane anesthesia by a single intraarticular injection of monosodium iodoacetate (3 mg/50 μL/rat) into one hind leg of each rat. EA was given at acupoints GB 30 and ST 36 on days 1-4 after the injection. Vehicle or ketanserin, a 5-HT2A/C receptor antagonist, was given intraperitoneally (1 mg kg(-1)) or intrathecally (5 μg or 10 μg/10 μL), 30 min before each EA treatment. Assessment of weight-bearing difference between injected and uninjected hind legs was done on days 0, 1-4 and 7. Fos /serotonin and serotonin/Fluorogold double labeling were performed to determine EA activation of serotonergic neurons in the nucleus raphe magnus (NRM) that project to spinal cord. The results showed that EA significantly decreases weight-bearing difference compared to sham EA. Ketanserin pretreatment blocked the analgesic effect of EA but did not influence weight bearing in sham EA control rats. EA also activated serotonergic NRM neurons that project to the spinal cord. These data show that EA inhibits osteoarthritis-induced pain by enhancing spinal 5-HT2A/2C receptor activity.

No MeSH data available.


Related in: MedlinePlus

Representative photograph showing the co-localization of serotonin and Fluorogold in the nucleus raphe magnus. (a) The 5-HT-immunoreactive neurons; (b) Fluorogold-labeled neurons projecting to the spinal cord; (c) Merged graphs of (a) and (b). Arrows indicate double-labeled 5-HT/Fluorogold neurons (yellow).
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fig5: Representative photograph showing the co-localization of serotonin and Fluorogold in the nucleus raphe magnus. (a) The 5-HT-immunoreactive neurons; (b) Fluorogold-labeled neurons projecting to the spinal cord; (c) Merged graphs of (a) and (b). Arrows indicate double-labeled 5-HT/Fluorogold neurons (yellow).

Mentions: Immunofluorescence double staining of serotonin and Fos demonstrated that EA induced Fos expression in the NRM (Figure 4(b)). Most EA-induced Fos was co-localized with serotonin (Figure 4(c)), which indicates that EA activated serotonergic neurons in this nucleus. Double staining of serotonin and the retrograde tracer Fluorogold, which was injected into the lumbar spinal cord, demonstrated that about 50% of NRM neurons that project to the spinal cord contained serotonin (Figures 5(a)–5(c)).


Serotonin Receptor 2A/C Is Involved in Electroacupuncture Inhibition of Pain in an Osteoarthritis Rat Model.

Li A, Zhang Y, Lao L, Xin J, Ren K, Berman BM, Zhang RX - Evid Based Complement Alternat Med (2011)

Representative photograph showing the co-localization of serotonin and Fluorogold in the nucleus raphe magnus. (a) The 5-HT-immunoreactive neurons; (b) Fluorogold-labeled neurons projecting to the spinal cord; (c) Merged graphs of (a) and (b). Arrows indicate double-labeled 5-HT/Fluorogold neurons (yellow).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139987&req=5

fig5: Representative photograph showing the co-localization of serotonin and Fluorogold in the nucleus raphe magnus. (a) The 5-HT-immunoreactive neurons; (b) Fluorogold-labeled neurons projecting to the spinal cord; (c) Merged graphs of (a) and (b). Arrows indicate double-labeled 5-HT/Fluorogold neurons (yellow).
Mentions: Immunofluorescence double staining of serotonin and Fos demonstrated that EA induced Fos expression in the NRM (Figure 4(b)). Most EA-induced Fos was co-localized with serotonin (Figure 4(c)), which indicates that EA activated serotonergic neurons in this nucleus. Double staining of serotonin and the retrograde tracer Fluorogold, which was injected into the lumbar spinal cord, demonstrated that about 50% of NRM neurons that project to the spinal cord contained serotonin (Figures 5(a)–5(c)).

Bottom Line: Acupuncture can benefit patients with knee osteoarthritis by providing pain relief, improving joint function and serving as an effective complement to standard care.However, the underlying mechanisms of its effects are still not completely understood.The results showed that EA significantly decreases weight-bearing difference compared to sham EA.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrative Medicine, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.

ABSTRACT
Osteoarthritis currently has no cure. Acupuncture can benefit patients with knee osteoarthritis by providing pain relief, improving joint function and serving as an effective complement to standard care. However, the underlying mechanisms of its effects are still not completely understood. The present study, an investigation of the effectiveness and mechanisms of electroacupuncture (EA) in attenuating osteoarthritis pain in a rat model, is focused on the involvement of 5-hydroxytryptamine 2A/C (5-HT2A/C) receptors, which play an important role in pain modulation at the spinal level. Osteoarthritis was induced under isoflurane anesthesia by a single intraarticular injection of monosodium iodoacetate (3 mg/50 μL/rat) into one hind leg of each rat. EA was given at acupoints GB 30 and ST 36 on days 1-4 after the injection. Vehicle or ketanserin, a 5-HT2A/C receptor antagonist, was given intraperitoneally (1 mg kg(-1)) or intrathecally (5 μg or 10 μg/10 μL), 30 min before each EA treatment. Assessment of weight-bearing difference between injected and uninjected hind legs was done on days 0, 1-4 and 7. Fos /serotonin and serotonin/Fluorogold double labeling were performed to determine EA activation of serotonergic neurons in the nucleus raphe magnus (NRM) that project to spinal cord. The results showed that EA significantly decreases weight-bearing difference compared to sham EA. Ketanserin pretreatment blocked the analgesic effect of EA but did not influence weight bearing in sham EA control rats. EA also activated serotonergic NRM neurons that project to the spinal cord. These data show that EA inhibits osteoarthritis-induced pain by enhancing spinal 5-HT2A/2C receptor activity.

No MeSH data available.


Related in: MedlinePlus