Tetraethylammonium-induced long-term potentiation in layer V horizontal connections of rat motor cortex

The possibility for the induction of long-lasting synaptic plasticity by th e potassium channel blocker tetraethylammonium (TEA) was investigated in ad ult rat motor cortex in vitro. Brief application of TEA (25 mM) resulted in a long-term potentiation (LTPK) of field potentials evoked in layer V intr alaminar connections by 59 +/- 17%. This effect could be prevented by prein cubation with nifedipine, a voltage-dependent calcium channel blocker (20 m uM), but not by N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-p hosphonovalerate (APV, 100 muM). LTPK induction resulted in a smaller relat ive potentiation of a response to the second pulse of a pair (60 ms interpu lse interval). These results indicate a potential of layer V horizontal con nections for a NMDA receptor-independent form of persistent synaptic enhanc ement. (C) 2001 Published by Elsevier Science Ireland Ltd.