ANXIOGENIC-LIKE EFFECTS OF TAGETES-MINUTA L ESSENTIAL OIL ON T-MAZE AND TONIC IMMOBILITY BEHAVIOR IN DOMESTIC CHICKS

In a first experiment, four doses (ranging between 0.04 and 0.45 mg/kg of body weight) of the essential oil from Tagetes minuta L. were subc utaneously injected in two-day-old chicks and a dose-response curve as sessed for escape performance in a T-maze test. The 0.1, 0.25 and 0.45 mg/kg doses impaired the first escape performance suggesting an anxio genic-like effect of the essential oil. After 3 h the same chicks were tested for a second escape performance, without being injected again, and no differences were observed compared to controls, suggesting tha t the essential oil did not affect retention. Furthermore, the effects of the essential oil were observed in the three sections of the T-maz e apparatus. So, the performance was impaired in the isolation chamber section, suggesting the induction of increased anxiogenic behaviour, and also in the mirror section, suggesting that the social reinstateme nt behaviour was modified by an increased anxiety level. Changes in th e principal corridor section were not observed, suggesting that the lo comotor activity was not affected by these oil doses. The second escap e performance was not affected in any of the T-maze sections, confirmi ng that these doses did not affect learning ability. In a second exper iment, a middle dose of the essential oil (0.25 mg/kg) increased the t onic immobility reaction in 15 days old chicks similarly to an anxioge nic dose of FG 7142 (1 mg/kg), while an anxiolytic dose of diazepam (0 .08 mg/kg) did not affect this behaviour. Taken together, the present results suggest that the essential oil from Tagetes minuta L. may exer t a negative modulation on the GABAergic function without affecting th e learning ability. (C) 1998 Elsevier, Paris.