BEHAVIORAL STRESS FACILITATES THE INDUCTION OF LONG-TERM DEPRESSION IN THE HIPPOCAMPUS

The induction of activity-dependent persistent increases in synaptic e fficacy, such as long-term potentiation (LTP), is inhibited by behavio ural stress(1,2). The question arises whether stress also affects the ability to induce persistent decreases in synaptic efficacy, such as l ong-term depression (LTD)(3-5). We now report that the induction of st able homosynaptic LTD in the CA1 area of the hippocampus of awake adul t rats is facilitated, rather than inhibited, by exposure to mild natu ralistic stress, The same stress blocked the induction of LTP, The eff ects of such stress were short lasting: acclimatization to, or removal from, the conditions that facilitated LTD induction led to a rapid lo ss of the ability to elicit this form of plasticity. The time window i n which LTD could be reliably elicited was prolonged by inducing anaes thesia immediately after the stress. These data reveal that even brief exposure to mild stress can produce a striking shift in the susceptib ility to synaptic plasticity in the awake animal.