["Unpredictable stress": Ambiguous Stress-Reactivity of Long-Term Plasticity].

The review considers possible mechanisms underlying large unpredictability of stress induced modulation of long-term synaptic plasticity. In studies of LTP, both increase and decrease can be observed dependently on stress paradigms, severity, duration, and period of recording, brain structure etc. Stress-induced glucocrti- coids release does not directly correlate with LTP changes, and corticosterone application in vivo andin vitro can either enhance or suppress LTP. The nature of stress induced modifications is usually explained by the balance between mineralocorticoid and glucocorticoid receptors, the later seems to provoke synaptic meta- plasticity rather than LTP disturbance, increasing the threshold of LTP induction. In addition, metaplasticity can be also modulated be many other neurotransmitters,'enhancing uncertainty and unpredictability of stress response, in particular because their action is highly regulated-by emotional experience.