Differential effects of ibotenic acid lesions of the hippocampus and blockade of N-methyl-D-aspartate receptor-dependent long-term potentiation on contextual processing in rats.
Good M., Bannerman D.
The contextual specificity of appetitive conditioned responding was examined in rats undergoing chronic intracerebroventricular infusion of 15 or 30 mM D-2-amino-5-phosphonopentanoic acid (D-AP5) or with excitotoxic hippocampal lesions. The magnitude of conditioned responding by control rats and rats infused with D-AP5 to a conditioned stimulus (CS) trained in Context A was attenuated when the same stimulus was presented in Context B. By contrast, hippocampal-lesioned rats displayed comparable levels of responding to the CS when presented in either Context A or B. Subsequent in vivo electrophysiological investigations showed that the D-AP5 concentrations were effective in blocking long-term potentiation (LTP) in the dentate gyrus. Results indicate that rats are capable of processing contextual information in the absence of N-methyl-D-aspartate (NMDA) receptor-dependent LTP and demonstrate an important dissociation between the effects of hippocampal lesions and the blockade of NMDA receptors in the hippocampus.