Evidence for Different Neurochemical Contributions to Long-term Potentiation and to Kindling and Kindling-induced Potentiation: Role of NMDA and Urethane-sensitive Mechanisms

Long-term potentiation (LTP) and kindling share a number of features, and it has been suggested that LTP might constitute the cellular mechanism of kindling. This question was approached by assessing the effect of urethane anesthesia (0.75 or 1.5 g/kg) or blockade of NMDA receptors by local infusion of DL-2-amino-5-phosphonovaleric acid (APV; 7.5 micrograms) on LTP, partial kindling, and kindling-induced potentiation (KIP) in the perforant path-dentate gyrus circuit of the intact hooded rat. Urethane anesthesia attenuated but did not block LTP and completely blocked partial kindling and KIP. APV completely blocked LTP but did not block partial kindling or KIP in the unanesthetized rat. These results suggest that different neurochemical mechanisms can support LTP on the one hand, and kindling and KIP on the other. They are consistent with a contribution by NMDA-mediated LTP to kindling and KIP, but they indicate that this contribution is not crucial for kindling and KIP in this circuit.