Are Ca(2+)-permeable kainate/AMPA receptors more abundant in immature brain?
The permeability properties of kainate/AMPA receptors are determined by subunit composition. The GluR1 and GluR3 subunits form Ca(2+)-permeable channels and exhibit inward rectification; heteromeric receptors containing the GluR2 subunit are Ca(2+)-impermeable and electrically linear. These observations raise the possibility of a developmental 'switch' in which turning on or off of GluR2 expression regulates the level of Ca2+ permeable kainate/AMPA receptors. We examined the ratio of GluR1 and GluR3 to GluR2 gene expression in developing and adult rat brain by in situ hybridization. A larger value of this ratio is likely to be associated with greater Ca2+ permeability. Our data suggest that in neocortex, striatum and cerebellum the number of Ca(2+)-permeable kainate/AMPA receptors is high at P4 and declines monotonically with age. In hippocampus, the number increases from P7 to P21, after which it declines. These findings provide evidence for a developmental 'switch' in which Ca2+ permeable glutamate receptors are turned off following early developmental events.
Pellegrini-Giampietro
D E
DE
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461.
Bennett
M V
MV
Zukin
R S
RS
D000375:Aging / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000254:growth & development*; D001923:Brain Chemistry / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002454:Cell Differentiation; D017403:In Situ Hybridization; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D002118:Calcium; D015220:Calcium Channels; D015347:RNA Probes; D012333:RNA, Messenger; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D017981:Receptors, Neurotransmitter