ANATOMICAL PLASTICITY IN THE MEDIAL SUPERIOR OLIVE FOLLOWING ABLATIONOF THE INFERIOR COLLICULUS IN NEONATAL AND ADULT-RATS

Citation
S. Okoyama et al., ANATOMICAL PLASTICITY IN THE MEDIAL SUPERIOR OLIVE FOLLOWING ABLATIONOF THE INFERIOR COLLICULUS IN NEONATAL AND ADULT-RATS, Hearing research, 88(1-2), 1995, pp. 71-78
Citations number
34
Categorie Soggetti
Neurosciences,Acoustics
Journal title
ISSN journal
03785955
Volume
88
Issue
1-2
Year of publication
1995
Pages
71 - 78
Database
ISI
SICI code
0378-5955(1995)88:1-2<71:APITMS>2.0.ZU;2-L
Abstract
We evaluated the consequences of unilateral ablation of the inferior c olliculus (IC) upon the ascending projection from the medial superior olive (MSG) to the IC. Ablation of the IC was performed in rats aged b etween postnatal day 1 (P1) and maturity. All the rats were given inje ctions of Fluoro-Gold (FG) into the ipsilateral IC at birth (PO) (befo re the ipsilateral IC was ablated in any case) so that growth of early -developing axons to the ipsilateral IC could be examined for any labe led neurons in the ipsilateral MSG. Upon reaching adulthood, the rats received injections of Fluoro-Ruby (FR) into the contralateral (intact ) IC so that aberrant crossed projections to the intact IC could be ex amined for any labeled neurons in the ipsilateral MSG. These rats were killed 2 days after FR injections. The number of surviving cells in t he ipsilateral MSO were counted in Nissl-stained sections for quantita tive analysis of retrograde degeneration. The results show that: (1) t he total number of neurons was reduced to 64-34% in the ipsilateral MS O as a result of IC ablation; (2) cell reduction by retrograde degener ation followed a U-shaped curve with a maximal effect in rats operated at P7 (reduced to 34%); (3) adult ablation of the IC led to retrograd e degeneration that was less severe than that in late neonatal (P7) ab lation; (4) an aberrant projection from the MSO to the contralateral I C occurred in rats operated at P1 and P3 but not in rats operated at P 7 or maturity. Thus, our findings suggest that growth of late-developi ng axons is a major factor in the plasticity of this system of project ion.