NR2A subunit transcription-traduction after LTP induction.

M V BAEZ; M CERCATO; M V OBERHOLZER; A I AGUIRRE; D A JERUSALINSKY

Washington

Congreso; SfN Annual Meeting; 2011

SfN

SfN 2011  NR2A subunit transcription-traduction after LTP induction. Baez MV1; Cercato M1,3; Oberholzer MV1,2; Aguirre AI1,2; Jerusalinsky D1,2. 1Instituto de Biología Celular y Neurociencias, CONICET-UBA, Buenos Aires, Argentina. 2 Universidad de Buenos Aires, Buenos Aires, Argentina. 3Universidad de Quilmes, Quilmes, Argentina. NMDA receptors (NMDAR) are tetramers containing two NR1 subunits and two NR2 and/or NR3 subunits. Depending on the NR2 composition, NMDAR changes its functional characteristics. In the rat hippocampus, major NR2 subunits are NR2A and NR2B. At early stages of postnatal development NR2B expression is more abundant than NR2A, but at mature synapses NR2A becomes predominant. Belloni and Nicoll (2007) have reported that LTP induction in rat hippocampal pyramidal cells of P2 or P9, produced kinetic change in voltage clamp recordings and modified the sensitivity to an NR2B selective antagonist (ifenprodil). These results were interpreted as a rapid decrease in NR2B-containing NMDAR and an increase in NR2A-containing NMDAR at the cell surface. This switch was attributed to a rapid increase in NR2B endocytosis whereas NR2A containing receptors delivery to the synaptic membrane increases. However, little is known about the expression (transcription-translation) of the NR2 subunits after LTP induction in young and adult rats. To evaluate NMDAR subunit expression after LTP induction, field potential recordings were performed in hippocampal fresh slices of young adult rats (P42-60) with a 0.033Hz stimulation for 3 h. LTP was induced by a theta burst stimulation protocol. After electrophysiology, these slices were analyzed by westernblot in order to determine NR1, NR2A and NR2B expression. Preliminary results showed a slight increase in the expression of NR1 and NR2B 30 min after LTP induction. Furthermore, 70 min after LTP induction, there were conspicuous increases in NR1 and NR2A expression (about 6 and 5 fold, respectively). Immunofluorescence assays in primary hippocampal neurons culture have shown that the increase in NMDAR subunits predominantly occurred at the level of dendrites and synapses. These findings support the hypothesis for a direct involvement of postsynaptic NMDARs in LTP establishment and maintenance.