Quantitative changes in calretinin immunostaining in the cochlear nuclei after unilateral cochlear removal in young ferrets.
Neurons of the cochlear nuclei receive axosomatic endings from primary afferent fibers from the cochlea and have projections that diverge to form parallel ascending auditory pathways. These cells are characterized by neurochemical phenotypes such as levels of calretinin. To test whether or not early deafferentation results in changes in calretinin immunostaining in the cochlear nucleus, unilateral cochlear ablations were performed in ferrets soon after hearing onset (postnatal day [P]30-P40). Two months later, changes in calretinin immunostaining as well as cell size, volume, and synaptophysin immunostaining were assessed in the anteroventral (AVCN), posteroventral (PVCN), and dorsal cochlear nucleus (DCN). A decrease in calretinin immunostaining was evident ipsilaterally within the AVCN and PVCN but not in the DCN. Further analysis revealed a decrease both in the calretinin-immunostained neuropil and in the calretinin-immunostained area within AVCN and PVCN neurons. These declines were accompanied by significant ipsilateral decreases in volume as well as neuron area in the AVCN and PVCN compared with the contralateral cochlear nucleus and unoperated animals, but not compared with the DCN. In addition, there was a significant contralateral increase in calretinin-immunostained area within AVCN and PVCN neurons compared with control animals. Finally, a decrease in area of synaptophysin immunostaining in both the ipsilateral AVCN and PVCN without changes in the number of boutons was found. The present data demonstrate that unilateral cochlear ablation leads to 1) decreased immunostaining of the neuropil in the AVCN and PVCN ipsilaterally, 2) decreased calretinin immunostaining within AVCN and PVCN neurons ipsilaterally, 3) synaptogenesis in the AVCN and PVCN ipsilaterally, and 4) increased calretinin immunostaining within AVCN and PVCN neurons contralaterally.
Fuentes-Santamaria
Verónica
V
Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1010, USA. vfuentes@fubmc.edu
Alvarado
Juan Carlos
JC
Taylor
Anna R
AR
Brunso-Bechtold
Judy K
JK
Henkel
Craig K
CK
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western / Q000379:methods; D064032:Calbindin 2; D002452:Cell Count / Q000379:methods; D003051:Cochlea / Q000294:innervation / Q000502:physiology / Q000601:surgery*; D017626:Cochlear Nucleus / Q000166:cytology* / Q000378:metabolism; D003952:Diagnostic Imaging / Q000379:methods; D005289:Ferrets; D007839:Functional Laterality / Q000502:physiology; D007150:Immunohistochemistry / Q000379:methods; D016571:Neural Networks, Computer; D009474:Neurons / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D016708:Synaptophysin / Q000378:metabolism
D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G; D016708:Synaptophysin