Figure 10.

The persistent firing response of AOB mitral cells involves TRPM4 channels. A, The ratio between AOB and MOB mRNA levels of five TRP candidate genes. TRPM4 shows the most significant difference with approximately twofold higher mRNA level in the AOB. Results average three independent experiments, each done in triplicate. B, Immunohistochemical staining of AOB (left) and MOB (right) slices to TRPM4. Although both structures show TRPM4 expression in the soma of their mitral cells (yellow arrows, higher magnification below), only the AOB shows intense signal in the glomerular layer (red arrows), most likely because of TRPM4 expression in the dendritic tufts of the mitral cells. C, D, Typical voltage responses of an AOB mitral cell to injection of EPSC-like currents (80 pA) in the absence (C) and presence (D) of 9-phenanthrol (100 μm) in the intracellular solution. E, Mean PSTHs of the responses of eight AOB cells (7 animals) recorded before (blue) and during (red) the presence of 9-phenanthrol (100 μm) in the bath solution. The TRPM4 blocker significantly reduces the prolonged firing response of the cells. F, Mean voltage trajectories of the responses analyzed in E in both conditions. The trajectory fell significantly faster in the presence of 9-phenanthrol.