WAY 100635, a 5-HT1A receptor antagonist, prevents the impairment of spatial learning caused by blockade of hippocampal NMDA receptors

We studied the effect of WAY 100635, a 5-HT1A receptor antagonist, on the impairment of spatial learning caused by intrahippocampal injection of 3-((R)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), a competitive NMDA receptor antagonist, in a two-platform spatial discrimination task. CPP, 3 and 10 ng/mu l, administered bilaterally into the CA1 region of the dorsal hippocampus 10 min before each training session, dose-dependently reduced choice accuracy in the two-platform spatial discrimination task with little or no effect on choice latency and errors of omission. A volume of 10 ng/mu l intrahippocampal CPP did not affect choice accuracy or latency of a non-spatial visual discrimination task. Subcutaneous doses of 0.3 and 1 mg/kg WAY 100635 did not modify the choice accuracy, but prevented the impairment caused by 10 ng/mu l intrahippocampal CPP. A dose of 20 ng/mu l WAY 100635 into the dorsal hippocampus prevented the deficit caused by 10 ng/yl CPP administered in the same region. The results suggest that blockade of 5-HT1A receptors can compensate the loss of NMDA-mediated excitatory input to pyramidal cells in the hippocampus. These findings may have clinical relevance for the symptomatic treatment of memory disorders associated with reduced glutamate transmission mediated by NMDA receptors. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.