DARPP32 is a D1-receptor associated signaling
protein found in striatal projection neurons in
mammals, including both substance P-containing (SP+) neurons and enkephalinergic (ENK+) projection neurons. The present
study used immunohistochemical single- and
double-labeling to examine the cellular localization of DARPP32 in pigeon
striatum. Single-label studies revealed that DARPP32 is present in numerous
medium-sized striatal perikarya
and DARPP32+ axons and terminals were seen to profusely innervate the two major
striatal projection targets, the pallidum
and the substantia nigra.
The single-labeling studies indicated that about 60% of all striatal
perikarya labeled for DARPP32+ in striatum, which
exceeds the abundance of either SP+ or ENK+ perikarya.
Single-labeling studies also showed that the abundance of DARPP32+ fibers and
terminals in pallidum exceeds that of either SP+ or
ENK+ fibers and terminals in pallidum.
Double-labeling found that 30-50% of striatal SP+ perikarya and 7-24% of ENK+ striatal
perikarya labeled for DARPP32 in pigeon, and
confirmed that DARPP32 was found in both SP+ and ENK+ fibers and terminals in pallidum. In contrast to its prevalence in striatal projection neurons, DARPP32 was virtually absent
from cholinergic and NPY+ striatal interneurons, as also true in mammals. Our data are
consistent with the interpretation that many SP+ neurons and many ENK+ neurons
in avian striatum possess D1-type dopamine receptors and use a DARPP32 signalling pathway, although this may be more common for
SP+ than for ENK+ neurons.
PMID: 9924970 [PubMed - indexed for MEDLINE