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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

Effect of an i.t. ketanserin injection on EA analgesia. Ketanserin at 10 μg pretreatment significantly blocked the analgesic effect of EA on days 2–7 after iodoacetate. There is no significant difference between the 5 μg and vehicle groups. *P < .05, **P < .01, ***P < .001 versus vehicle control.
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fig3: Effect of an i.t. ketanserin injection on EA analgesia. Ketanserin at 10 μg pretreatment significantly blocked the analgesic effect of EA on days 2–7 after iodoacetate. There is no significant difference between the 5 μg and vehicle groups. *P < .05, **P < .01, ***P < .001 versus vehicle control.

Mentions: As shown in Figure 3, rats given EA plus 10 μg of i.t. ketanserin put significantly less weight on the ipsilateral leg than did rats with EA plus vehicle on days 2 (23.5 ± 2.7 versus 38.1 ± 2.5, P < .01), 3 (18.9 ± 1.4 versus 37.3 ± 3.9 versus, P < .001), 4 (22.5 ± 3.1 versus 38.8 ± 2.8, P < .01) and 7 (32.9 ± 3.6 versus 44.6 ± 1.8, P < .05). Weight bearing was not significantly different between rats given EA plus 5 μg of ketanserin and those given EA plus vehicle, although the former showed a slightly greater ability to bear weight. This indicates that EA may inhibit pain by inducing serotonin release in the spinal cord.


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)

Effect of an i.t. ketanserin injection on EA analgesia. Ketanserin at 10 μg pretreatment significantly blocked the analgesic effect of EA on days 2–7 after iodoacetate. There is no significant difference between the 5 μg and vehicle groups. *P < .05, **P < .01, ***P < .001 versus vehicle control.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig3: Effect of an i.t. ketanserin injection on EA analgesia. Ketanserin at 10 μg pretreatment significantly blocked the analgesic effect of EA on days 2–7 after iodoacetate. There is no significant difference between the 5 μg and vehicle groups. *P < .05, **P < .01, ***P < .001 versus vehicle control.
Mentions: As shown in Figure 3, rats given EA plus 10 μg of i.t. ketanserin put significantly less weight on the ipsilateral leg than did rats with EA plus vehicle on days 2 (23.5 ± 2.7 versus 38.1 ± 2.5, P < .01), 3 (18.9 ± 1.4 versus 37.3 ± 3.9 versus, P < .001), 4 (22.5 ± 3.1 versus 38.8 ± 2.8, P < .01) and 7 (32.9 ± 3.6 versus 44.6 ± 1.8, P < .05). Weight bearing was not significantly different between rats given EA plus 5 μg of ketanserin and those given EA plus vehicle, although the former showed a slightly greater ability to bear weight. This indicates that EA may inhibit pain by inducing serotonin release in the spinal cord.

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