Excitatory and inhibitory purinergic control of neck muscle nociception in anaesthetized mice

Authors


Professor Dr. med. Dr. med. habil. Jens Ellrich, Centre for Sensory-Motor Interaction SMI, Department of Health Science and Technology, Medical Faculty, Aalborg University, Fredrik Bajers Vej 7D2, DK-9220 Aalborg, Denmark. Tel. + 45 9940-9896, fax + 45 9815-4008, e-mail jellrich@hst.aau.dk

Abstract

Tension-type headache is associated with noxious input from neck muscles. Due to the importance of purinergic mechanisms in muscle nociception, experimental studies typically inject α,β-methyleneadenosine 5′-triphosphate (α,β-meATP). In contrast to native adenosine 5′-triphosphate (ATP), α,β-meATP has a narrow receptor profile and remains stable in tissue. The present study administered α,β-meATP or ATP in semi-spinal neck muscles in anaesthetized mice (n = 65) in order to address different effects in neck muscle nociception. The jaw-opening reflex monitored the impact of neck muscle noxious input on brainstem processing. Injection of α,β-meATP induced reflex facilitation in a dose-dependent manner. In contrast, only the lowest ATP dosage evoked facilitation. Preceding P2Y1 receptor blockade revealed facilitation even under high-dosage ATP. Ongoing facilitation after α,β-meATP injection neutralized under subsequent activation of P2Y1 receptors. Results demonstrate opposing excitatory P2X and inhibitory P2Y effects of ATP in neck muscle nociception. These mechanisms may be involved in the pathophysiology of neck muscle pain in man.

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