Figure 7

Transgenic mouse expressing synaptopHluorin (spH) in mitral and tufted cells. (A, B) Fluorescence of whole-mount brain of Tbx-spH transgenic mouse viewed from ventral (A) and lateral side (B). (C₁-C₃) spH signal increase in the piriform cortex is dependent on the pulse numbers of electrical stimulation onto olfactory bulb (OB) glomeruli. ΔF/F fluorescence change images (C₁), time course (C₂) and pulse-response relationship (C₃). (D₁, D₂) spH signal increase is dependent on the amplitude of electrical stimulation onto OB glomeruli. Time course (D₁) and amplitude-response relationship (D₂). (E₁-F₃) spH signal increase upon the electrical stimulation of trimethylthiazoline (TMT; E₁-E₃) and heptanoic acid (HA)-responsive (F₁-F₃) glomeruli. Odourant-responsive glomeruli were identified by the intrinsic signal imaging of the dorsal surface of OB and stimulated with a microelectrode (E₁, F₁). The electrical stimulation of these two glomeruli leads to the spH signal increase in distinct subregions of the piriform cortex (E₂, E₃, F₂, F₃). (G₁) Similarity and dissimilarity between fluorescent responses evoked by the OB electrical microstimulation. The imaged region was divided into four subregions (APCd, APCv, PPCd, PPCv: dorsal and ventral parts of the anterior and posterior piriform cortex) [40, 43]. Significantly responsive areas (P < 0.01, yellow-to-red areas in E_2-3 and F_2-3) evoked by electrical stimulation of TMT- and HA-responsive glomeruli were plotted (n = 3). (G₂) Cluster analysis of spH responses. The linkage distance was 4.95 ± 1.70 between any two TMT stimulation images and 22.4 ± 4.53 between any two HA stimulation images. In contrast, the distance between any TMT stimulation image and any HA stimulation image was significantly larger (58.0 ± 1.95; P< 0.00001). (H₁, H₂) spH signal increase in the piriform cortex upon odourant stimulation. TMT (H₁) or HA (H₂) applied into mouse nostril leads to the spH signal increase in overlapping but distinct regions of the piriform cortex.