The Effect of Taurine on Excitatory Receptor Binding in Rat Hippocampal Membranes

Abstract

Recent reports have shown that L-³H glutamate binds with high affinity to hippocampal membranes (12). Moreover, this binding is increased by CaCl₂ (1), although it is still under discussion whether the calcium increase is mediated by chloride ions (11,16). Many authors suggest that Ca²⁺ can activate neutral protease (2) and that the activity of these proteases could be responsible for learning and memory capability (10). Taurine is a molecule that is able to reduce L-glutamate-induced depolarization in isolated frog spinal cord (7) and to abolish the after-hyperpolarization induced by L-glutamate (8). Moreover, it reduces acquisition of avoidance conditioned reflex (14) and decreases acquisition and, to a lesser extent, retention of a step-down passive avoidance task (13). In the nervous system, taurine interacts with calcium. In fact, 25 mM taurine increases the high affinity Ca²⁺ binding to rat hippocampal membranes but has no effect on low affinity Ca²⁺ uptake to rat brain synaptosomes (6).