Terbium fluorescence characteristics of cultured neurons using ultraviolet microspectrofluorometry

The fluorescence emission intensity of terbium is enhanced upon the binding of Tb3+ to cultured mouse spinal cord and dorsal root ganglion neurons, via nonradiative resonant energy transfer from membrane proteins. The relative fluorescence intensities of Tb3+ bound to dorsal root ganglion neurons were considerably greater than that of Tb3+ bound to large multipolar spinal cord neurons. The cell bodies of the dorsal root ganglion neurons were completely covered in a dense fluorescent blanket, where as the fluorescence from the spinal cord soma presented a discontinuous pattern. The neurites of the spinal cord neuron were speckled with bright patches of Tb3+ fluorescence. A high concentration of Ca2+ reduced the relative fluorescence intensity of the Tb3+-neuron complex. It is suggested that Tb3+ binds to Ca2+-binding sites on the surface membrane of neurons.