Hippocampus is one of the important sites for mammalian learning and memory, and Long-term potentiation (LTP) is a potential neurophysiological mechanism responsible for learning and memory.Despite several in vitro studies indicate that glutamate (Glu) and its ionotropic receptors involved in the hippocampal LTP, however, little is known about the underlying neurophysiological mechanisms of hippocampal learning-dependent LTP in conscious and freely moving animals.In this work, glutamate receptor antagonists MK-801and CNQX were locally microinjected into the hippocampal CA 1 region, then the extracellular concentration of Glu and amplitude of the field excitatory postsynaptic potential (fEPSP)-LTP in CA 1 region were measured during the period of establishment and experimental extinction of the conditioned reflex in conscious rats.