Opposite effects of lanthanum on different types of nicotinic acetylcholine receptors

The effects of lanthanum (La3+) were studied on muscle and neuronal nicotinic acetylcholine receptors (AChRs) expressed in Xenopus oocytes. La3+ exerts a dose-dependent positive modulation on alpha1 beta1 gamma8 muscle AChRs, whereas it modulates negatively either alpha2 beta2, alpha2 beta4 or alpha3 beta4 neuronal AChRs. Moreover, La3+ appears to accelerate the desensitization of neuronal receptors. In both muscle and neuronal AChRs, the respective potentiating or inhibiting effects of La3+ on the ACh-currents are voltage-independent, suggesting that La3+ is acting at a site located in the external domain of the receptor.