Fig. 4. The effects of BDNF on AMPA currents are TrkB-mediated. A, TrkB immunoreactivity in the commissural subnucleus of the nucleus tractus solitarius in a P0 rat (transverse section). Scale bar, 100 μm. In control sections in which the primary antibody was omitted during the staining procedure, no staining was detected above background (data not shown).B, TrkB-positive (large arrow) and TrkB-negative (small arrow) cell in a P0 nTS culture, 24 hr after plating. Scale bar, 20 μm. C, Sample recording of the AMPA currents measured in a P0 nTS neuron during control AMPA application (AMPA) and during the coapplication of AMPA and BDNF after 1 min BDNF pretreatment (AMPA + BDNF), before (Control) and after K252a treatment. The cell was superfused with 200 nm K252a for 12 min. Calibration: 4 sec, 50 pA. D, Mean integrated currents in P0 nTS neurons evoked by control 2 sec application of AMPA alone (AMPA control), AMPA, and BDNF after 1 min BDNF pretreatment (AMPA + BDNF), and after return to superfusion with control bath solution (AMPA recovery) in the absence or presence of 200 nm K252a; n= 8. E, Mean integrated currents in four P0 nTS neurons in which the effects of 200 nm K252b on BDNF inhibition of AMPA currents were tested. AMPA responses were abolished by BDNF in all neurons tested before and after K252b treatment.