Anatomical and ultrastructural characterization of the frog accessory olfactory bulb and vomeronasal nerve
| dc.contributor.author | Merx, Xander | |
| dc.date.accessioned | 2026-05-13T15:59:27Z | |
| dc.date.available | 2026-05-13T15:59:27Z | |
| dc.date.issued | 2026 | |
| dc.description.abstract | The accessory olfactory bulb (AOB) serves as the central relay for vomeronasal chemosensory information and has been implicated in activity-dependent synaptic plasticity in frogs. Activity-dependent enhancement (ADE), observed at the vomeronasal nerve (VNN)–mitral cell synapse, has been described in Rana pipiens and hypothesized to involve neuropeptide co-release from dense-core vesicle (DCV)-containing afferent terminals. Bimodal compound action potential recordings from the Lithobates catesbeiana VNN suggest the presence of two morphologically distinct axon populations. The present study employed light microscopy, transmission electron microscopy (TEM), and horseradish peroxidase (HRP) anterograde tracing to characterize the anatomy and ultrastructure of the AOB and VNN in adult L. catesbeiana. Light microscopy revealed a laminated AOB with glomerular and mitral cell layers; a notably sparse periglomerular cell population was identified, consistent with the frog AOB being less elaborated than its mammalian counterpart. TEM of the glomerular neuropil identified likely dendrodendritic synapses and gap junctions, features documented in the mammalian olfactory bulb but not previously reported in the frog AOB. Large vesicular profiles with electron-dense cores were observed in HRP-DAB labeled VNN afferent terminals; however, the evidence is insufficient to confirm the presence of dense-core vesicles, and these observations do not provide anatomical support for the neuropeptide co-release hypothesis. Quantitative axon diameter analysis identified two morphologically distinct fascicle types: Type A fascicles with a unimodal small-axon distribution and Type B fascicles with a bimodal distribution with a sparse large-profile subpopulation, consistent with the bimodal CAP profile. These structural observations support ongoing functional investigations and warrant further study using biochemical and volumetric imaging approaches. Supervisor: Dr. Kerry Delaney | |
| dc.description.reviewstatus | Unreviewed | |
| dc.description.scholarlevel | Undergraduate | |
| dc.identifier.uri | https://hdl.handle.net/1828/23887 | |
| dc.language.iso | en | |
| dc.publisher | University of Victoria | |
| dc.subject.department | Department of Biology | |
| dc.title | Anatomical and ultrastructural characterization of the frog accessory olfactory bulb and vomeronasal nerve | |
| dc.type | Honours thesis |