Anxiolytic- and anxiogenic-like effects of Montanoa tomentosa (Asteraceae): Dependence on the endocrine condition.

Ethnopharmacological Relevance: Montanoa tomentosa Cerv. (MT) is a native plant from Mexico used in traditional medicine as a remedy for reproductive impairments and relaxing effects. In previous studies, it has been shown that the endocrine state could modify the antianxiety-like actions of anxiolytic compounds. Although women are the primary user of MT, no studies have evaluated the potential impact of the endocrine milieu on its anti-anxiety actions.

Aims Of The Study: Ascertain the antianxiety effects of M. tomentosa in rats with different hormonal conditions, and to analyze the participation of the GABA receptor in ovariectomized rats treated with MT.

Materials And Methods: The animal model of anxiety used was the elevated plus-maze (EPM). Rats' endocrine conditions were: a) Low hormone levels (rats in diestrus I and II phases); b) High hormone levels (proestrus/estrus phases); c) No hormones (ovariectomized rats); and d) Rats under progesterone withdrawal (PW). To evaluate the participation of the GABA receptor in the anxiolytic-like action of MT the antagonist picrotoxin was used.

Results: Results showed that MT induced dose-dependent anxiolytic-like actions in rats with low hormone level conditions. Also, MT reduced anxiety-like behavior in female rats under PW, in contrast to diazepam which was ineffective. MT's anxiolytic-like effect was blocked by picrotoxin, suggesting the participation of the GABA receptor complex. However, increased anxiety-like behavior was observed in rats with a high hormone level condition and low doses of MT.

Conclusions: Beneficial anxiolytic-like actions of MT are observed under low hormone conditions, particularly in the PW challenge (a condition that can be related to a premenstrual period). Furthermore, the participation of the GABA receptor is evidenced. However, hormonal variations could induce the opposite effects, hence women should be cautious.