Abstract:
Essential oils have been widely used for various medicinal purposes, including
relaxation and memory enhancement. A number of studies have shown that they have
various effects on the nervous system. Lavender fragrance for example is used to
improve sleep patterns, and reduce aggression. Another kind of essential oil frequently
used in aromatherapy is jasmine oil which has been found to promote EEG beta waves
thereby showing the stimulating effect of this fragrance. Ylang-ylang oil is also used
as an antidepressant and has been shown to increase attention. However, the
importance of essential oils for learning and memory is less well documented. The aim
of this study was to investigate the effects of jasmine, lavender, and ylang-ylang
essential oils on spatial learning in mice. ICR Mice were randomly divided into three
essential oil treated groups and one control group. Each group comprised eight mice.
Housing and testing were carried out at different places to avoid odorant
contamination on the control group. 15 μl of pure essential oil were sprayed on to
cotton balls and were attached covered cages refreshed every 2 days. ICR mice were
exposed to essential oils for 20 days, and then their spatial learning capability in the
Morris water maze was analysed using the Ethovision (Noldus Information
Technology, Netherlands) video tracking system. Following the behavioral study,
animals were perfused and their brains were collected. Brain serial sections were
reconstructed, and analyzed by SGI O2 running software Micro3D (version 2004;
NeSys, Oslo, Norway). In the behavioral study, jasmine oil-treated mice took a
significant the shorter path length and time to find the hidden platform in the water
maze compared to the control group. Lavender and ylang-ylang treated mice also took
slightly shorter times to find the platform compared to the controlled mice. The
jasmine treated group had a significantly larger hippocampal volume than the control
group. By contrast, the lavender treated group showed a significantly decreased
hippocampal volume compared to the control group. In addition, volumes of left and
right hippocampus were not significantly different in all conditions. Nevertheless,
there was no significant different in hippocampal volume between male and female
mice. This study suggests that jasmine, and perhaps ylang-ylang oil, might enhance
spatial learning in mice.