Rapid changes in light-scattering in the prism of Torpedo electric organ slice associated with the production of postsynaptic potentials

Using a bifurcated lightguide placed on the surface of a prism of the electric organ slice of Torpedo, the generation of postsynaptic potentials by direct stimulation was found to be associated with readily detectable, disphasic optical changes. The changes consisted of a decrease in light-scattering during the rising phase of the electric potential, followed by a prolonged increase in scattering. The effects of varying the calcium-ion concentration in the medium strongly support the view the replacement of transmitter molecules for bound Ca-ions in the receptor proteins is at the base of these changes. The effects of synaptically active reagents on these optical signals were demonstrated.