Ev. Gurevich et al., Thalamo-cortical afferents control transient expression of the dopamine D-3 receptor in the rat somatosensory cortex, CEREB CORT, 11(8), 2001, pp. 691-701
The D-3 dopamine receptor (D3R) is selectively and transiently expressed in
the barrel neurons of the somatosensory cortex (SI) between the first and
second postnatal weeks. The D3R expression starts after the initial ingrowt
h of thalamocortical afferents (TCAs) into the barrel cortex and could be i
nduced or controlled by them. We show that unilateral electrolytic lesion o
f the thalamic ventrobasal complex immediately after birth leads to a decre
ase in the D3R mRNA concentration in the lesioned SI 7 days after the lesio
n, whereas the D3R binding is little affected, Fourteen days after the neon
atal thalamic lesion, the D3R binding and mRNA are drastically reduced and
the barrel-like pattern of the D3R is absent. Elevation of the D-3 binding
normally seen between the first and second postnatal weeks does not occur.
Thalamic lesion on P6 differentially affects the D3R expression. One day af
ter the lesion, the D-3 binding and mRNA are down-regulated, but the effect
is transient. Five days after the lesion the concentration of D-3 mRNA in
the lesioned hemisphere returns to the control level. The typical barrel-li
ke pattern of D3R expression is evident in the lesioned S1, although TCAs a
re completely absent. Quantitative analysis demonstrated elevated cellular
levels of the D-3 mRNA in barrel neurons 5 days after the lesion. These hig
her levels are needed, perhaps, to support the increased production of the
D3R protein appropriate for this age, Age-related dynamics of the D3R bindi
ng is retained in the lesioned S1, although the concentration of D3R sites
remains reduced. These data demonstrate that intact thalamic input is essen
tial for the formation of mechanisms responsible for developmental regulati
on of the D3R expression in the SI.