Effects of olfactory stimulation by α-pinene on autonomic nervous activity

Wood has been used as building material and for making furniture since a long time, and it has been known from experience that woody smell acts as a mood relaxant. Several studies on the physiological and psychological effects of wood or wood-derived smells have been conducted [ 1 – 7 ]. The inhalation of air containing volatile organic compounds released from the interior walls of Japanese cedar suppresses increases in salivary chromogranin A [ 1 ]. Olfactory stimulation by Japanese cedar chips decreases systolic blood pressure and prefrontal cortex activity [ 2 ]. Olfactory stimulation by air-dried wood chips of Japanese cypress, which is commonly found and is widely used as a building material in Japan, reduced the oxygenated hemoglobin concentration in the prefrontal cortex [ 3 ]. Moreover, it has been reported that staying at night in a hotel room filled with the smell of Japanese cypress essential oil for three consecutive nights induces natural killer cell activity and reduces the concentrations of adrenaline and noradrenaline in urine [ 4 ]. Olfactory stimulation by the essential oil from Japanese cypress leaf enhances parasympathetic nervous activity and decreases prefrontal cortex activity; in a subjective evaluation, the stimulation was assessed to be “comfortable” [ 5 ]. Inhalation of d -limonene, which is a major component of conifer wood extracts such as Japanese cedar and Japanese cypress, enhanced parasympathetic nervous activity and decreased heart rate; in a subjective evaluation, the stimulation was also assessed to be “comfortable” [ 6 ]. Inhalation of cedrol, a compound found in cedar extract, induced parasympathetic nervous activity and reduced sympathetic nervous activity [ 7 ].