Reinnervation of the rat olfactory bulb after methyl bromide-induced lesion

Timing and extent of reinnervation

James E. Schwob, Steven Youngentob, George Ring, Carrie L. Iwema, Renee C. Mezza

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

We used the inhalation of methyl bromide gas to produce a near-complete destruction of the rat olfactory epithelium and analyzed the reinnervation of the bulb during reconstitution of the epithelium. The degeneration of olfactory axons elicits a transient up-regulation of glial cell proliferation and glial fibrillary acidic protein expression in the olfactory nerve and olfactory nerve layer of the bulb. Anterograde transport after intranasal infusion of wheat germ agglutinin conjugated horseradish peroxidase demonstrates that the first nascent axons reach the bulb within the first week after lesion. Subsequently, a massive wave of fibers arrives at the bulb between 1 and 2 weeks postlesion, and enters the glomeruli between 2 and 3 weeks postlesion. However, the olfactory projection does not stabilize until 8 weeks after lesion judging from the return in growth associated protein-43 expression to control levels. The extent of reinnervation after lesion is correlated with the completeness with which the epithelium reconstitutes itself. In rats that are lesioned while fed ad libitum, there is near- complete reconstitution of the neuronal population, and the projection onto the bulb fills the glomerular layer in its entirety. However, in rats that are lesioned while food restricted, a significant fraction of olfactory epithelium becomes respiratory during its reconstitution, and the population of reinnervating fibers is less. As a consequence, the posterior half of the bulb remains hypoinnervated overall and denervated at its caudal margin. The preferential reinnervation of the anterior bulb in the food-restricted, methyl bromide gas-lesioned animals indicates that the mechanisms that guide the growth of the olfactory axons and restore receptotopy do not operate with the same precision in this setting as they do during development or during the lower level of turnover associated with the 'normal' laboratory existence. Accordingly, we hypothesize that the persistence of a significant population of pre-existing neurons is needed to preserve receptotopy during reinnervation. In addition, the results suggest that in the face of massive turnover and a reduced afferent population, there is a tendency for reinnervating axons to fill available synaptic space.

Original languageEnglish (US)
Pages (from-to)439-457
Number of pages19
JournalJournal of Comparative Neurology
Volume412
Issue number3
DOIs
StatePublished - Sep 27 1999
Externally publishedYes

Fingerprint

methyl bromide
Olfactory Bulb
Axons
Olfactory Nerve
Olfactory Mucosa
Epithelium
Gases
Population
GAP-43 Protein
Food
Wheat Germ Agglutinins
Glial Fibrillary Acidic Protein
Horseradish Peroxidase
Neuroglia
Inhalation
Up-Regulation
Cell Proliferation
Neurons
Growth

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)

Cite this

Reinnervation of the rat olfactory bulb after methyl bromide-induced lesion : Timing and extent of reinnervation. / Schwob, James E.; Youngentob, Steven; Ring, George; Iwema, Carrie L.; Mezza, Renee C.

In: Journal of Comparative Neurology, Vol. 412, No. 3, 27.09.1999, p. 439-457.

Research output: Contribution to journalArticle

Schwob, James E. ; Youngentob, Steven ; Ring, George ; Iwema, Carrie L. ; Mezza, Renee C. / Reinnervation of the rat olfactory bulb after methyl bromide-induced lesion : Timing and extent of reinnervation. In: Journal of Comparative Neurology. 1999 ; Vol. 412, No. 3. pp. 439-457.
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