Behavioural Responses And Expression Of P2X3 Receptor

archives of oral biology 54 (2009) 63–70

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Behavioural responses and expression of P2X3 receptor in trigeminal ganglion after experimental tooth movement in rats
Zhi Yang a,1, Yang Cao b, Yan Wang a,1, Wei Luo c, Xiaochuan Hua a, Yun Lu a, Zhengyu Liao a,1, Wenli Lai a,*, Zhihe Zhao a
aState Key Laboratory of Oral Diseases and Department of Orthodontics, West China College of Stomatology, Sichuan University, Chengdu, China b Department of Orthodontics, Zhongshan University, China c Department of Orthodontics, Hangzhou Stomatology Hospital, Zhejiang, China

article info
Article history: Accepted 7 September 2008 Keywords: Experimental tooth movement Trigeminal ganglion PainDirected face-grooming

abstract
Objective: To explore the role of P2X3 receptor in pain induced by experimental tooth movement. Design: Male Sprague-Dawley rats weighing 200–300 g were used. P2X3 receptor distribution in the caudal one-third portion of the trigeminal ganglion (TG) was studied by IHC. Next, the changes of P2X3 expression were detected by Western blotting 4 h, 1 d, 2 d, 3 d, 5 d, 7 d,14 d after tooth movement. We then developed a behaviour pain model associated with directed mouth wiping. Finally, the effect of TNP-ATP on nociceptive-like behaviour was evaluated. Results: Our results showed that P2X3 receptors were expressed mainly in small- and medium-sized cells and experimental tooth movement led to an increase in staining of mandibular P2X3 receptors. In addition,following experimental tooth movement, the expression of P2X3 receptor in TG was statistically significantly up-regulated from days 1 to 5, with a peak on day 3. It was also found that the time spent on directed mouth wiping was dramatically increased by experimental tooth movement from days 1 to 7. The rhythm change of P2X3 receptor expression in TG and the mouth wiping behaviour were in concert with theinitial orthodontic pain responses. The directed mouth wiping behaviour was modulated in a force-dependent manner and could be attenuated by peripheral and systemic morphine. Furthermore, peripherally administered TNP-ATP could exert an analgesic effect on this pain model. Conclusion: These results suggest that directed mouth wiping behaviour can be a reliable measurement of pain followingexperimental tooth movement in rats. The P2X3 receptor is important in the development and maintenance of tooth movement pain and thus may be peripheral targets for analgesics in orthodontic pain control. # 2008 Elsevier Ltd. All rights reserved.

* Corresponding author at: Department of Orthodontics. No. 14, Section 3, Ren Min Nan Road, Chengdu, China. Tel.: +86 28 85503645; fax: +86 28 85502332.E-mail addresses: Wenlilai@hotmail.com, wcums1981@tom.com (W. Lai).
1 Ph.D. candidate. 0003–9969/$ – see front matter # 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2008.09.003

64 1. Introduction

archives of oral biology 54 (2009) 63–70

Orthodontic tooth movement is induced by mechanical force and facilitated by remodelling of the periodontal ligament (PDL) andalveolar bone. Inflammatory actions occur mainly in the PDL inclined to tooth movement. The orthodontic force affects the tooth pulp and gingiva, inducing vascular changes which are inflammatory in nature.1 Patients always perceive pain and discomfort during tooth movement and this is one of the most troublesome problems encountered by Orthodontists clinically,2 especially at the early stages of treatment.In the trigeminal somatosensory system, periodontal tissues are mainly innervated by primary sensory neurones in the trigeminal ganglion (TG).3 Branches of the trigeminal nerve are particularly vulnerable to inflammatory responses in periodontal tissues during tooth movement. The trigeminal ganglion plays an important role in orofacial pain transmission. ATP is now recognised as an important...