Afferent influences on brain stem auditory nuclei of the chicken: neuron number and size following cochlea removal

• Published in: Journal of comparative neurology (1911) Vol. 231; no. 4; p. 435
• Main Authors: Born, D E, Rubel, E W
• Format: Journal Article
• Language: English
• Published: United States 22.01.1985
• Subjects: Age Factors; Animals; Auditory Pathways - pathology; Brain Stem - pathology; Cell Count; Chickens; Cochlear Nerve - injuries; Time Factors
• ISSN: 0021-9967
• DOI: 10.1002/cne.902310403

The consequences of cochlea removal on neuron number and soma cross-sectional area were examined in the second order auditory nucleus (n. magnocellularis) of chickens. Both the age of the subjects at the time of cochlea (basilar papilla) removal (1-66 weeks) and the survival period (1-45 days) were varied. Neuron number and soma cross-sectional area were determined from Nissl stained sections. Additional material was processed to examine the relationship of ganglion cell loss to changes in n. magnocellularis. Neuron number decreased by 25-30% and soma cross-sectional area decreased by 10-20% ipsilateral to the cochlea removal in chickens operated on during the first 6 weeks after hatching. In contrast, in chickens operated on at 66 weeks posthatch neuron number decreased less than 10% and there was no change in soma area. The changes were rapid, being nearly complete 2 days after cochlea removal. An initial change (1 and 2 days after surgery) observed in animals operated on up to 6 weeks posthatch was the presence of a large number of neurons in which no Nissl substance could be detected. These results demonstrate an age-dependent change in the susceptibility of NM neurons to deafferentation. This change is not temporally related to other measures of functional maturation of the auditory system.