Em. Finney et Cj. Shatz, ESTABLISHMENT OF PATTERNED THALAMOCORTICAL CONNECTIONS DOES NOT REQUIRE NITRIC-OXIDE SYNTHASE, The Journal of neuroscience, 18(21), 1998, pp. 8826-8838
Subplate neurons are early-generated neurons that project into the ove
rlying neocortex and are required for the formation of ocular dominanc
e columns. A subset of subplate neurons express nitric oxide synthase
(NOS) and produce nitric oxide (NO), a neuronal messenger thought to b
e involved in adult hippocampal synaptic plasticity and also in the es
tablishment of certain specific connections during visual system devel
opment. Here, we examine whether the NOS-containing subplate neurons a
re involved in ocular dominance column formation in the ferret visual
system. Ocular dominance columns form in ferrets between postnatal day
35 (P35) and P60. NOS expression in the visual subplate is low at bir
th, increases to a maximum at the onset of ocular dominance column for
mation, and falls thereafter. Nevertheless, blockade of NOS with daily
injections of nitroarginine from P14 to P56 fails to prevent the form
ation of ocular dominance columns, although NOS activity is reduced by
>98%. To test further a requirement for NOS in the patterning of conn
ections during CNS development, we examined the cortical barrels in th
e somatosensory system of mice carrying targeted disruptions of NOS th
at also received injections of nitroarginine; cortical barrels formed
normally in these animals. In addition, barrel field plasticity induce
d by whisker ablation at birth was normal in nitroarginine-injected NO
S knock-out mice. Thus, despite the dynamic regulation of NOS in subpl
ate neurons, NO is unlikely to be essential for the patterning of thal
amocortical connections either in visual or somatosensory systems.