BACKGROUND AND AIMS: Maternal separation (MS) of rat pups has been widely used to study the mechanisms underlying the effects of early life stress on the adult organism. Such stress has been shown to induce alterations in the functions of the amygdala, a structure which plays a key role in the acquisition, consolidation and retrieval of fearrelated memories. Our previous study has revealed that in the cortical input (CoI) to the lateral amygdala (LA) MS has shifted the potential for bidirectional synaptic modification towards LTD, but it shrank the synaptic modification range in the thalamic input (ThI) to the LA. Since imipramine (IMI) has been reported to reverse some effects of stress on the cerebral cortex, here we studied whether the effects of MS on the LA could be reversed by IMI. METHODS: Rat pups were subjected to MS (3 h/day) on postnatal days (PND) 1–21 and weaned at PND 28. On PND 29–42 males previously subjected to MS were administered IMI (10 mg/kg/ 2 ml). Control rats received saline. On PND 43–60 brain slices containing the LA were prepared and field potentials were recorded. Saturating levels of LTP or LTD were induced using repeated sequences of theta-burst stimulation or low frequency stimulation. RESULTS: Both LTP and LTD were reduced in ThI in slices obtained from MS-subjected rats receiving saline when compared to controls. However, in slices prepared from MS-subjected rats receiving IMI the magnitude of LTP and LTD wassimilar to control preparations obtained from non-stressed rats. In CoI the magnitude of LTP in slices prepared from stressed rats administered IMI was still smaller, when compared to control rats receiving saline or IMI, but the magnitude of LTD was similar to controls. These results confirm that MS alters the synaptic modification range both in ThI and CoI to LA. CONCLUSIONS: Treatment with IMI fully reversed the effects of MS in the thalamic input. In the cortical input the reversal was only partial. Support: National Science Center, Poland, grant no. 2011/03/N/ NZ4/02176.
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