Neuropharmacological actions of some binuclear lanthanide(III) complexes.

Binuclear lanthanide(III) compounds are of great interest because of the potential of their mutual Ln(3+)-Ln(3+) electronic couplings to produce unusually sharp images in magnetic resonance and fluorescence imaging of biological tissue. The toxicity and neuropharmacological properties of the water soluble and stable neutral binuclear complex [La(api)](2) were compared with those of binuclear complexes with lower water stability, and the components used in their syntheses. The order of the 24-h LD(50) (mg/kg body wt.) of the compounds in mice was: salicylaldehyde (2.24)<H(3)api (32.3)<[La(2) L(1) (NO(3))(4)].H(2)O (35.1)<triethylenetetramine (38.5)<La(2) L(2)(NO(3))](2) (43.4)<La(NO(3))(3).5H(2)O=[GdL(3) (NO(3))](2) (45.7)<La(2)L(4) (NO(3))(4).CH(3)OH (49.6)<[La (api)](2) (>160). These compounds induced convulsions, urination and defecation in mice. Due to the relatively very low toxicity of [La(api)](2), its mode of action was explored. Its proconvulsant action may possibly involve an interaction of undissociated complex with muscarinic receptors, and is reversed by atropine.