Resin glycosides evoke the Gaba release by sodium- and/or calcium-dependent mechanism

Ipomoea tyrianthina Lindley (syn. I. orizabensis Pelletan, Lebed. ex Steud., Convolvulaceae) is known as a purgative, but it has been also used in Mexican traditional medicine in the treatment of seizures and pain for their anticonvulsive, hypnotic and sedative properties. Some glycolipids isolated from this plant have shown significant effects on Central Nervous System, modifying inhibitory or excitatory processes. The mechanism for such activity it is not clear; studies with these metabolites have suggested that a pore-forming mechanism is involved in their activity. Therefore, the present work explores a possible not pore-forming mechanism related to the effect of four resin glycosides, Scammonin 1 (S-1), tyrianthin C (T-C), tyrianthin A (T-A) and tyrianthinic acid VI (TA-VI), isolated from Ipomoea tyrianthina root on GABAergic transmission system in cerebral cortex slices of mouse brain in an in vitro model. The results obtained show that all glycolipids tested evoked endogenous GABA release and increased its concentration within the incubation medium compared with controls; T-C demonstrated a dose-dependent effect. Sodium absence and guvacine presence did not affect significantly the activity of S-1 and T-C in contrast to T-A and TA-VI. S-1 and T-C effects were calcium-dependent, where GABA concentrations were considerably reduced. These results suggest that the increase of endogenous γ-aminobutyric acid (GABA) released evoked by these glycolipids is possibly done through a Na⁺- and/or Ca²⁺-dependent mechanisms, discarding a pore-forming mechanism.