The aroma of lavender must be one of the best known and the biological activity of the vapour from the essential oil has been investigated in several species including man. As early as 1920, Plant looked at the actions of 'waters' of lavender on intestinal activity in the dog and a year later Macht and Ting (1921) reported on the sedative action of the vapour from tincture of lavender on rats. More recently, Buchbauer's group in Vienna have performed detailed experiments on mice and humans (Buchbauer et al, 1993).
Triebs (1956) and Sticher (1977) have reviewed the results from early experiments on some of the constituents of lavender, which is one of the oils reviewed by Tisserand and Balacs (1995) in their guide on the safety of essential oils.
142 Stephen Hart and Maria Lis-Balchin Experiments in vivo
Lavender oil and its component, linalool, produce a fall in blood pressure in experimental animals probably due to peripheral vasodilatation (Tisserand and Balacs, 1995).
Macht and Ting (1921) trained rats to negotiate a maze to find food and then determined the effect of exposure to the vapour from essential oils on the time taken to reach the food and the number of errors occurring. Most of their experiments were on valerian and various incense, but three rats were exposed to a tincture of lavender and in each case the time to reach the food doubled, with two animals also making errors in the maze. From these results is was concluded by the authors that lavender had a slight sedative action and it was suggested that the vapour from essential oils might be stimulating olfactory sense organs directly. Delaveau et al. (1989) administered lavender essence (L. angustifolia P. Miller) orally to mice and observed changes in activity to electrical stimulation, which were interpreted as an anxiolytic effect. In addition, it was shown that lavender essence enhanced the hypnotic action of pentobarbitone. Such an effect on barbiturate sleeping time may indicate an effect on the brain but could also be due to inhibition of liver enzymes which metabolise barbiturates. The sedative action of lavender is confirmed by the work of Buchbauer et al. (1991) who, like Macht and Ting (1921), studied the effects of the vapour rather than the oil administered orally. Buchbauer et al. (1991) exposed mice to the vapour from lavender (L. angustifolia Mill.), and the components linalool and linalyl acetate, and found a reduction in overall activity, as monitored in activity boxes. Scores in the activity box are increased when mice are pre-treated with caffeine given by the intraperitoneal route and this increase in activity is very sensitive to inhibition by lavender oil, linalool and linalyl acetate (Buchbauer et al., 1993). Interestingly, exposure of mice to the vapour from linalool led to measurable levels of the compound in their plasma. The authors considered that the sedative action is due to the absorption of linalool and its subsequent transport to the brain by the blood, rather than a direct stimulation of olfactory receptors. Results from experiments in mice and rats thus confirm that lavender is a sedative.
Elisabetsky et al. (1995) report that linalool produces a dose-dependent inhibition of the binding of glutamate (an excitatory neurotransmitter in the brain) to its receptors on membranes prepared from the cerebral cortex of the rat, which is a possible explanation for the observed sedative effects. More recently, Elisabetsky et al. (1999) have related this action to an anticonvulsant activity of linalool in rats. Lavender is one of the few essential oils that have been studied in well-controlled experiments in humans. Buchbauer et al. (1993) measured two types of reaction times in male and female students breathing either air or vapour from the essential oil of lavender. Reaction times were increased by lavender and it was possible to show that this was not due to a peripheral effect but to central sedation. Attempts have also been made to monitor the effects of inhaled essential oils on blood flow through the brain using computerised tomography. Buchbauer et al. (1993) observed no changes with lavender oil or linalyl acetate but a decrease with 1,8-cineol. It has also been reported that the vapour of lavender essential oil reduces certain brain waves (contingent negative variation, CNV) in humans (Torii et al, 1988; Manley, 1993).
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You have probably heard the term Aromatherapy and wondered what exactly that funny word, „aromatherapy‟ actually means. It is the use of plant oils in there most essential form to promote both mental and physical well being. The use of the word aroma implies the process of inhaling the scents from these oils into your lungs for therapeutic benefit.