Acute intraperitoneal administration of lanthanum chloride to newborn chicks at the single dose of 250 mg/kg body weight inhibits calcium binding to brain synaptosomal membrane. There is also marked depression in the activities of neural Ca2+-ATPase, Mg2+-ATPase, and cholinesterase after acute lanthanum chloride intoxication. The inhibition of these enzymes in relation to depletion of calcium binding to the synaptosomal membrane has been discussed. © 1982.