Rhinotopy is disrupted during the re-innervation of the olfactory bulb that follows transection of the olfactory nerve

• Published in: Chemical senses Vol. 26; no. 4; pp. 359 - 369
• Main Authors: CHRISTENSEN, Marc D, HOLBROOK, Eric H, COSTANZO, Richard M, SCHWOB, James E
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.05.2001; Oxford Publishing Limited (England)
• Subjects: Animals; Antibodies, Monoclonal - analysis; Axons - physiology; Biological and medical sciences; Cell Adhesion Molecules, Neuronal - metabolism; Cell Surface Extensions - physiology; Fundamental and applied biological sciences. Psychology; Male; Nerve Regeneration - physiology; Neural Cell Adhesion Molecules; Olfactory Bulb - pathology; Olfactory Bulb - physiopathology; Olfactory Mucosa - innervation; Olfactory Mucosa - metabolism; Olfactory Nerve - metabolism; Olfactory Nerve - pathology; Olfactory Nerve Injuries; Olfactory system and olfaction. Gustatory system and gustation; Rats; Rats, Sprague-Dawley; rhinotopy; Vertebrates: nervous system and sense organs; Wounds, Stab - physiopathology; Animal model; Rodentia; Central nervous system; Rattus norvegicus; Transect method; Vertebrata; Mammalia; Olfactory pathway; Functional recovery; Investigation method; Olfactory nerve; Olfaction; Olfactory bulb; Reinnervation; Olfactory epithelium; Brain (vertebrata)
• ISSN: 0379-864X; 1464-3553; 1464-3553
• DOI: 10.1093/chemse/26.4.359

Re-innervation of the olfactory bulb was investigated after transection of the olfactory nerve using monoclonal antibody RB-8 to assess whether rhinotopy of the primary olfactory projection is restored. In normal animals RB-8 heavily stains the axons, and their terminals, that project from the ventrolateral olfactory epithelium onto glomeruli of the ventrolateral bulb (termed RB-8(+)). In contrast, axons from dorsomedial epithelium are unlabeled (RB-8(-)) and normally terminate in the dorsomedial bulb. Sprague-Dawley rats underwent unilateral olfactory nerve transection and survived for 6 weeks prior to perfusion, sectioning and immunostaining with RB-8. Nerve lesion does not shift the position of the boundary between RB-8(+) and RB-8(-) regions of the epithelium. However, following transection and bulb re-innervation, the distribution of RB-8(+) and RB-8(-) axons is markedly abnormal. First, in all 10 experimental animals RB-8(-) axons displace RB-8(+) axons from anterior glomeruli. Furthermore, the usual target of the RB-8(-) fibers, i.e. the dorsomedial bulb at more posterior levels of the bulb, remains denervated, judging by the lack of staining with antibodies that label axons derived from all epithelial zones. Finally, RB-8(+) fibers invade foreign territory in the dorsolateral bulb on the lesioned side in some cases. The shifts in terminal territory in the bulb after transection contrast with the restoration of the normal zonal patterning of the projection after recovery from methyl bromide lesion, but is consistent with reports of mistargeting by a receptor-defined subset of neurons after transection.