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Updated: Jul 23, 2026
Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections
Published on: November 14, 2016
Olfactory toxicity of beta,beta'-iminodipropionitrile in the rat
M B Genter1, J Llorens, J P O'Callaghan
1Department of Toxicology, North Carolina State University, Raleigh.
Abstract:
Following a pilot study which revealed olfactory epithelial degeneration induced by beta,beta'-iminodipropionitrile (IDPN), dose-response and time-course analyses were undertaken to further characterize the effects of IDPN on the olfactory system. Male rats were sacrificed at multiple time points ranging from 24 hr after a single dose to 56 days after three consecutive daily doses of IDPN (0-400 mg/kg i.p.). Nasal cavities were fixed, decalcified and embedded in paraffin; 5 microns sections were stained with hematoxylin and eosin, middle neurofilament protein antibody or olfactory marker protein antiserum. Olfactory bulbs were removed for slot blot analyses of glial fibrillary acidic protein, synapsin I and p38. Another group of rats was treated with saline or IDPN and perfused 6 hr or 1, 2, 3, 7, 14 or 28 days after the last dose. Olfactory bulb axonal degeneration was visualized using a modified Gallyas technique. Twenty-four hours after treatment with 200 or 400 mg/kg IDPN, there was severe, highly site-specific mucosal degeneration in the dorsal-medial nasal cavity; regeneration was incomplete 8 weeks later. IDPN increased olfactory bulb glial fibrillary acidic protein, peaking 7 days after three daily 400 mg/kg doses, and remaining significantly elevated 8 weeks after treatment. Olfactory bulbs contained substantial silver deposition in afferent axon bundles in the glomerular layer, beginning 24 hr after the first dose and persisting for 14 days after dosing. Although only a portion of the olfactory epithelium was damaged by IDPN, all axon bundles entering the olfactory bulb were involved, suggesting the lack of a clear topographic arrangement of sensory endings in the olfactory bulb.
Insights
Beta,beta'-iminodipropionitrile (IDPN) causes severe olfactory epithelial degeneration in rats, with incomplete regeneration and persistent olfactory bulb changes. This neurotoxin impacts the entire olfactory bulb axonal system, regardless of the initial damage site.
Area of Science:
- Neuroscience
- Toxicology
- Histopathology
Background:
- Olfactory epithelial degeneration was previously observed following beta,beta'-iminodipropionitrile (IDPN) exposure.
- Further characterization of IDPN's effects on the olfactory system is needed.
Purpose of the Study:
- To conduct dose-response and time-course analyses of IDPN's impact on the rat olfactory system.
- To investigate the extent of olfactory epithelial damage and subsequent regeneration.
- To evaluate changes in the olfactory bulb following IDPN exposure.
Main Methods:
- Rats received varying doses of IDPN (0-400 mg/kg i.p.) and were sacrificed at different time points.
- Nasal cavities were sectioned and stained for histological analysis.
- Olfactory bulbs underwent slot blot analysis for specific proteins and silver staining for axonal degeneration.
Main Results:
- Severe, site-specific olfactory mucosal degeneration occurred within 24 hours post-IDPN (200-400 mg/kg), with incomplete regeneration by 8 weeks.
- IDPN significantly increased olfactory bulb glial fibrillary acidic protein, peaking at 7 days and remaining elevated for 8 weeks.
- Axonal degeneration in olfactory bulb afferent bundles was observed from 24 hours to 14 days post-IDPN, affecting all bundles.
Conclusions:
- IDPN induces significant and persistent damage to the olfactory epithelium and bulb in rats.
- The neurotoxin affects all olfactory bulb afferent axons, irrespective of the localized epithelial damage.
- These findings suggest a potential disruption in the topographic organization of olfactory sensory input.
