Blockade of NMDA receptors decreased spinal microglia activation in bee venom induced acute inflammatory pain in rats

• Published in: Neurological research (New York) Vol. 39; no. 3; p. 271
• Main Authors: Li, Li, Wu, Yongfang, Bai, Zhifeng, Hu, Yuyan, Li, Wenbin
• Format: Journal Article
• Language: English
• Published: England 04.03.2017
• Subjects: Acute Pain - chemically induced; Acute Pain - prevention & control; Animals; Bee Venoms - administration & dosage; Bee Venoms - pharmacology; Behavior, Animal - drug effects; Disease Models, Animal; Dizocilpine Maleate - administration & dosage; Dizocilpine Maleate - pharmacology; Excitatory Amino Acid Antagonists - administration & dosage; Excitatory Amino Acid Antagonists - pharmacology; Male; Microglia - metabolism; Nociceptive Pain - chemically induced; Nociceptive Pain - prevention & control; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Spinal Cord Dorsal Horn - metabolism; spinal cord; rat; NMDA receptor; microglia; bee venom; peripheral inflammatory pain
• ISSN: 1743-1328
• DOI: 10.1080/01616412.2017.1281198

Microglial cells in spinal dorsal horn can be activated by nociceptive stimuli and the activated microglial cells release various cytokines enhancing the nociceptive transmission. However, the mechanisms underlying the activation of spinal microglia during nociceptive stimuli have not been well understood. In order to define the role of NMDA receptors in the activation of spinal microglia during nociceptive stimuli, the present study was undertaken to investigate the effect of blockade of NMDA receptors on the spinal microglial activation induced by acute peripheral inflammatory pain in rats. The acute inflammatory pain was induced by subcutaneous bee venom injection to the plantar surface of hind paw of rats. Spontaneous pain behavior, thermal withdrawal latency and mechanical withdrawal threshold were rated. The expression of specific microglia marker CD11b/c was assayed by immunohistochemistry and western blot. After bee venom treatment, it was found that rats produced a monophasic nociception characterized by constantly lifting and licking the injected hind paws, decreased thermal withdrawal latency and mechanical withdrawal threshold; immunohistochemistry displayed microglia with enlarged cell bodies, thickened, extended cellular processes with few ramifications, small spines, and intensive immunostaining; western blot showed upregulated expression level of CD11b/c within the period of hyperalgesia. Prior intrathecal injection of MK-801, a selective antagonist of NMDA receptors, attenuated the pain behaviors and suppressed up-regulation of CD11b/c induced by bee venom. It can be concluded that NMDA receptors take part in the mediation of spinal microglia activation in bee venom induced peripheral inflammatory pain and hyperalgesia in rats.