I. Rajan et Ht. Cline, GLUTAMATE-RECEPTOR ACTIVITY IS REQUIRED FOR NORMAL DEVELOPMENT OF TECTAL CELLS DENDRITES IN-VIVO, The Journal of neuroscience, 18(19), 1998, pp. 7836-7846
Glutamatergic retinotectal inputs mediated principally by NMDA recepto
rs can be recorded from optic tectal neurons early during their morpho
logical development in Xenopus tadpoles. As tectal cell dendrites elab
orate, retinotectal synaptic responses acquire an AMPA receptor-mediat
ed synaptic component, in addition to the NMDA component. Here, we tes
ted whether glutamatergic activity was required for the elaboration of
dendritic arbors in Xenopus optic tectal neurons. In vivo time-lapse
imaging of single Dil-labeled neurons shows that the NMDA receptor ant
agonist APV (100 mu M) blocked the early development of the tectal cel
l dendritic arbor, whereas the AMPA receptor antagonist CNQX (20 mu M)
or the sodium channel blocker TTX (1 mu M) did not. The decreased den
dritic development is attributable to failure to add new branches and
extend preexisling branches. These observations indicate that NMDA-typ
e glutamatergic activity promotes the initial development of the dendr
itic arbor. At later stages of tectal neuron development when AMPA rec
eptor-mediated synaptic transmission is strong, both APV and CNQX decr
ease dendritic arbor branch length, consistent with a role for glutama
tergic synaptic transmission in maintaining dendritic arbor structure,
These results indicate that AMPA and NMDA receptors can differentiall
y influence dendritic growth at different stages of neuronal developme
nt, in correlation with changes in the relative contribution of the re
ceptor subtype to synaptic transmission.