Effects of the NMDA antagonist 2AP5 on complex spike discharge by hippocampal pyramidal cells.

The N-methyl-D-aspartate receptor antagonist D,L-2-amino-5-phosphonopentanoate (2AP5) was administered intraventricularly to determine its effect on the complex spike firing pattern of spontaneously active hippocampal pyramidal cells recorded in urethane anaesthetized rats. Following 2AP5 delivery, complex spike firing decreased by a mean 36%, while only a 5% decrease was observed after saline injection. This effect could not be explained by changes in firing rate per se but appeared to be related to the degree of blockade of commissurally induced long-term potentiation. Thus 2AP5 not only disrupts synaptic plasticity in the hippocampus but can also alter the pattern of ongoing activity of the pyramidal cells.