Auditory nerve input is not an absolute requirement for the expression, distribution and calcium permeability of AMPA receptors in the adult rat ventral cochlear nucleus.
In order to understand whether glutamatergic excitatory presynaptic input is an absolute requirement for the adult regulation of postsynaptic glutamate receptors we analyzed if a period of 11 days of excitatory deprivation affects the expression, distribution and Ca(2+) permeability of AMPA receptor subunits in the ventral cochlear nucleus of the rat. Bilateral cochlear ablations were performed in 30-day-old rats. After 11 days of survival, immunohistochemistry for GluR1, GluR2/3 and GluR4 AMPA receptor subunits showed no changes in the normal pattern of distribution, with GluR2/3 and GluR4 immunoreactivity predominating, and little GluR1. No changes in the amount of these AMPA receptor subunits were found between normal and cochleotomized rats in Western blots. AMPA receptors lacking the GluR2 subunit are Ca(2+) permeable. Kainate-induced Co(2+) uptake histochemistry, which labels AMPA Ca(2+) permeable receptors, demonstrated no changes in somatic labeling intensity for Co(2+), 11 days after cochleotomy. Therefore, our data indicate that excitatory input is not an absolute requirement to maintain AMPA receptor subunit expression, distribution and functional properties such as Ca(2+) permeability in VCN neurons. Nevertheless, subtle changes in AMPA receptors through regulatory post-transductional mechanisms cannot be ruled out.
Martinez-Galan
Juan Ramon
JR
Facultad de Medicina and Centro Regional de Investigación Biomédica, Universidad de Castilla-La Mancha, Avenida de Almansa 14, 02006, Albacete, Spain.
Caminos
Elena
E
Vale
Carmen
C
Juiz
Jose M
JM
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D003056:Cochlear Nerve / Q000502:physiology*; D017626:Cochlear Nucleus / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D010539:Permeability; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000378:metabolism*; D014018:Tissue Distribution
D020033:Protein Isoforms; D018091:Receptors, AMPA; D002118:Calcium