Fig. 8: SPR knockdown in OSNs reveals heterogeneous SPR expression across glomeruli enables non-uniform MIPergic modulation of OSN ACV responses.
a Individual MIPergic LNs (magenta) significantly co-innervate several ACV-responsive glomeruli (cyan). Moreover, ACV-responsive OSNs (cyan) form synaptic connections with MIPergic LNs (magenta) and express the MIP receptor, SPR (turquoise). b Representative pseudocolored heatmaps of OSN GCaMP responses (∆F) before and during odor presentation in several test glomeruli (white dotted outlines) of animals where SPR is knocked down. In each case, each odor presentation heatmap pair is grouped by stage of MIP pharmacological application. Scale bar = 10 µm. c, d SPR knockdown in OSNs abolishes MIP-induced decrease in DM2 and DM5 OSN responses (DM2 10−2: p = 0.136, RM one-way ANOVA; 10−6: p = 0.063, pre-MIP vs. MIP & p = 0.688, pre-MIP vs. post-washout; Holm-adjusted Wilcoxon signed-rank test; n = 6; DM5 10−2: p = 0.135, RM one-way ANOVA; 10−6: p = 0.063, pre-MIP vs. MIP & p = 0.313, pre-MIP vs. post-washout; Holm-adjusted Wilcoxon signed-rank test; n = 6). In contrast, SPR knockdown in OSNs does not abolish MIP-induced increases in DM1 and DM4 OSN responses (DM1: p = 0.031, pre-MIP vs. MIP AUC; Holm-adjusted Wilcoxon signed-rank test; n = 7; DM4: p = 0.031, pre-MIP vs. MIP AUC; Holm-adjusted Wilcoxon signed-rank test; n = 7). In all cases: Data are presented as the mean (darker center line) ± SEM (lighter shaded area). Vertical and horizontal scale bars = 0.1 ∆F/F & one second (respectively). Odor onset is indicated by vertical lines running up each column of traces. Boxplots display the minimum, 25th-percentile, median, 75th-percentile, and maximum of the given data. Statistical measures of effect size (either Kendall’s W or Cohen’s d) are provided to the right of each set of AUC boxplots. All statistical tests were two-tailed. Glomerular schematics were derived from an in vivo AL atlas164. Source data are provided as a Source Data file. e Conceptual model of differential MIPergic modulation of OSN responses across multiple AL glomeruli. Our data suggests that the MIPergic LNs are the sole source of MIP to the AL, where MIP acts to directly decrease DM2 and DM5 OSN responses. Our data also suggest that MIP acts to indirectly increase DM1 and DM4 OSN responses, likely through disinhibition.
