Investigation of the Anxiolytic and Antidepressant Effects of Eucalyptol (1,8-Cineole), a Compound From Eucalyptus, in the Adult Male Sprague-Dawley Rat.

Anxiety and depression are debilitating, costly psychological disorders that account for $133 billion in direct medical expenses per year in the United States. Finding alternative means of treatment to reduce the personal and financial burden for patients with these disorders, while maintaining patient safety, is vital for overall patient wellness. The purposes of this study were 2-fold: (1) to determine if pure eucalyptol (1,8-cineole) produces anxiolytic and/or antidepressant effects using rat models for anxiety and behavioral despair and (2) to determine the effects of eucalyptol at the benzodiazepine site on the γ-aminobutyric acid (GABA) A receptor in the rat central nervous system. Fifty-five male Sprague-Dawley rats were randomly assigned to 1 of 5 groups: vehicle (dimethyl sulfoxide), eucalyptol, midazolam, flumazenil plus eucalyptol, and midazolam plus eucalyptol. Behavioral analyses were conducted on the elevated plus-maze and in the forced swim test. Data were analyzed using a 2-tailed multivariate analysis of variance and a least significant difference post hoc test. Data from the maze suggested eucalyptol may produce anxiolytic effects by acting at the benzodiazepine site on the GABA_A receptor while not affecting psychomotor activity. However, no effects on behavioral despair were demonstrated in the Forced Swim test.