The influence of vascular β-adrenoceptors on the position and mobility of the rabbit incisor tooth

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Abstract
The influence of vascular .beta.-adrenoceptors on the tooth-supporting functions of the periodontal ligament were studied in 30 anesthetized rabbits. Propranolol and the .beta.2-adrenoceptor antagonists ICI 118,551 [erythro-DL-1-(7-methylindan-4-yloxy)-3-isopropylamino butan-2-ol] and H 35/25 [.alpha.,4-dimethyl-N-isopropyl phenylethanolamine] induced a marked extrusion of the incisor, probably due to reduced vasodilator tone in peridontal postcapillary blood vessels. Isoprenaline reversed the movement. .beta.1- and .beta.2-receptor antagonists decreased the intrusive responses to sympathetic nerve stimulation in teeth close to control position, but had no effect on responses in fully extruded teeth. Intrusive mobility, as tested by intermittent loading with 5-10 g, remained unaffected by .beta.-adrenoceptor blockade. Vascular .beta.2-adrenoceptors are probably important in the regulation of tooth position by their control of periodontal postcapillary resistance. Prejunctional .beta.-receptors enhancing the vasoconstrictor- and intrusive-responses to sympathetic nerve stimulation are probably a mixture of .beta.1- and .beta.2-receptors. It would seem that the periodontal vasculature is important for the position of the rabbit tooth but, due to rapid adaptive mechanisms of the tooth-supporting tissues, the vasculature contributes little to the resistance against load-induced intrusive movements of the tooth.

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