Abscisic acid potentiates NMDA-gated currents in hippocampal neurones

NMDA receptor functioning underlies the basic mechanism of synaptic plasticity of the central nervous system. The NMDA receptor is a subject for modulation by certain substances: facilitation of this receptor is thought to be crucial for the induction of plasticity phenomena. In the present investigation evidence for a potentiation of the NMDA-receptor by trans,trans-abscisic acid (postulated endogenous substance) is provided. Pre-exposure to trans,trans-abscisic acid induced a marked increase mainly of the fast component of NMDA-gated currents in isolated rat hippocampal neurones. The potentiating effect depended on an extracellular trans,trans-abscisic acid concentration with an EC50 value about 440 microM, Hill coefficient 2. Such a facilitatory effect developed rather slowly with a time constant of about 3 s. The results obtained imply the existence of a novel mechanism of NMDA receptor potentiation. The data presented indicate a possible neurophysiological significance of abscisin.