A fuel pump apparatus is made free from the influence of height fluctuations of the surface of fuel in a fuel tank by providing a fuel inlet window in the side wall of a float chamber for containing a fuel gauge, which is provided inside the side wall of a housing. The accumulator bag, installed inside the cartridge, communicates with the external atmosphere through an air duct. Significantly, in vivo application of compounds of the instant invention established, on the basis of SSEP testing, that the compounds provide longer lasting effects at lower concentrations than comparable treatment with the known agent 4-aminopyridine. The pigments are useful as colorants, and possess good stability.