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
