Lack of correlation between the molecular size and the efficacy of lanthanides for potentiating GABAA currents in rat septal cholinergic neurons in culture

Actions of lanthanides were examined on GABAA receptor-activated responses in rat septal neurons in culture by using the whole-cell voltage-clamp technique. GABA (10 microM) currents were enhanced by these ions at 100 microM with an efficacy sequence of Pr3+ (1.11) > or = Lu3+ (1.07) > or = Gd3+ (1.02) > or = Er3+ (1.01) > or = La3+ (1: 40% increase) > or = Ce3+ (0.980) > or = Nd3+ (0.932) > or = Yb3+ (0.913) > or = Tb3+ (0.912), indicating the lack of correlation between the potentiating efficacy and ionic size of lanthanides.