OPPOSITE EFFECTS OF LANTHANUM ON DIFFERENT TYPES OF NICOTINIC ACETYLCHOLINE-RECEPTORS

THE effects of lanthanum (La3+) were studied on muscle and neuronal ni cotinic acetylcholine receptors (AChRs) expressed in Xenopus oocytes. La3+ exerts a dose-dependent positive modulation on alpha 1 beta 1 gam ma delta muscle AChRs, whereas it modulates negatively either alpha 2 beta 2, alpha 2 beta 4 or alpha 3 beta 4 neuronal AChRs. Moreover, La3 + appears to accelerate the desensitization of neuronal receptors. In both muscle and neuronal AChRs, the respective potentiating or inhibit ing effects of La3+ on the ACh-currents are voltage-independent, sugge sting that La3+ is acting at a site located in the external domain of the receptor.