Eucalyptus oil is frequently used in phytotherapy. The objective of the present paper was to investigate to what extent 1.8-cineole influences the activity of smooth muscle fibres. The effects of 1.8-cineole on the spontaneous contractile activity were investigated in in vitro experiments with circular smooth muscle fibres of guinea pig stomach. 1.8-cineole was found to have agonistic effects on the a1 and a2 adrenergic receptors. These effects can be registered at low concentrations of up to 3 × 10-7 to 2 × 10-5 M 1.8-cineole. At higher concentrations, the well-known spasmolytic effect appears. At concentrations above 4 × 10-4 M 1.8-cineole, the effect of 10-5 M acetylcholine is 100% suppressed. The results allow for the assumption that, besides the spasmolytic effects investigated to date and owing to its specific effects on the a2 adrenergic receptors of the nerve cells, 1.8-cineole brings about an additional improvement to local blood circulation and alleviates pain.
Key words: Smooth muscle fibre, 1.8-cineole (eucalyptol), a1 and a2 adrenergic receptors, papaverine, pain, clonidine.
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