Anticonvulsant and antidepressant activity of the selected terpene GABA derivatives in experimental tests in mice

The present study was designed to investigate the central nervous system activity of terpene GABA (and piracetam) derivatives designated as BF-1, BF-2, BF-3, BF-4, BF-5, BF-6. We assessed their anticonvulsant activity in the two main mouse models of seizures (MES-test, PTZ-test), an antidepressant-like effect in the forced swim test (FST), as well as an influence on spontaneous locomotor activity. Our study demonstrated the strong anticonvulsant activity of (1S,3R,7R)-(-)-3,8,8-trimethyl-4-aza-bicyclo[5.1.0]acetate-5-one hydrochloride (compound BF-2) in the PTZ-test. Activity of BF-2 was equipotent to ethosuximide (380 mg/kg, po) in the PTZ-test, when used at a dose of 100 mg/kg, po. No neurotoxic effects were demonstrated by administration of all tested compounds. Moreover, BF-2, BF-3, BF-6 compounds significantly reduced the immobility time in FST at both doses (by 21-50%), while BF-5 induced a significant anti-immobility effect only when used at a dose of 100 mg/kg (by 39%). The compound BF-6 used at the dose of 30 mg/kg was the most active (50% reduction), and the effect was similar to the result obtained with classical antidepressant--imipramine. The motor stimulatory activity was demonstrated by BF-1 compound at the dose of 100 mg/kg with no effect at a lower (30 mg/kg) dose. On the other hand, the BF-3 at 30 mg/kg significantly decreased spontaneous activity during 30 min observation period, while no alteration in this activity during 6-min observation was detected. At present, it is not possible to indicate which mechanisms of novel, active terpene GABA derivatives are involved in the demonstrated antidepressant-like activity. Although further studies are needed to solve this issue, these data suggest a potential value of the examined terpene GABA derivatives.