Figure 6.

Monosynatic feedback projections from CA1 hippocampus to the main olfactory bulb. (A) Widefield fluorescent image of an example of feedback projecting neurons from CA 1 to granule cells in the olfactory bulb (insert). Scale bar = 500 um. (B) 3D-reconstruction of hippocampus/CA 1 boundaries with retrogradely labeled neurons (red). Scale bar = 500 um (C) Normalized dorsal-ventral distribution of retrogradely labeled neurons in CA 1. (D1) Confocal image of CA 1 neurons. (D2) Reconstruction of neuronal morphology from cells in D1. Scale bar = 200 μm. (E) Example of densly labeled neurons in vCA 1. Gray lines = CA 1 boundary. Red dots = retrograde labeled neurons. (F1) Injection site in the bulb corresponding to CA 1 reconstruction in (E). GrMOB = Granule cells in main olfactory bulb (MOB). Red line corresponds to the accessory olfactory bulb (AOB) boundary. (E2) Enlargement of AOB from E1. GrAOB = Granule cells of AOB. (G) Reconstruction of all sections of the MOB injection from (E1). Black dots = labeled neurons in MOB. Red dots = labeled neurons in AOB. Gray lines = granule cell layer boundary. (H) Distribution of labeled cells along the rostral-caudal axis (normalized) for MOB (black) and AOB (red) in left and ratio of MOB to AOB cells for densly labeled injection sites (right). CTX-B = cholera toxin B subunit. (K,L) Correspond to subsequent panels. (J) Schematic for anterograde label of axons projecting to the MOB from vCA 1. (K) CTX-B injection into CA 1. (L1) MOB with axonal arbors from CA 1 injection. (L2) Enlargement of G2 shows feedback processes from CA 1. Scale bar = 50 μm.