Unmasking adenosine 2A receptors (A2ARs) in monkey basal ganglia output neurons using cholera toxin subunit B (CTB).
The A(2A)R has become a therapeutic target in Parkinson disease due to its functional role in the striatum, capable of modulating dopaminergic neurotransmission in the basal ganglia. No conclusive evidence, however, has been provided to demonstrate the existence of A(2A)Rs in the output nuclei of the basal ganglia: the internal segment of the globus pallidus (GPi) and substantia nigra pars reticulata (SNr). Using immunohistochemistry and in situ hybridization techniques we have confirmed the presence of A(2A)Rs in both the striatum (medium spiny and cholinergic neurons) and the external segment of the globus pallidus (GPe), in the monkey. The antibody routinely used to label A(2A)Rs failed to detect A(2A)R-positive neurons in the GPi and SNr, however, in situ hybridization showed that A(2A)R mRNA transcripts were indeed present in both these nuclei. Surprisingly, by labeling pallidothalamic and nigrothalamic projection neurons originating in the GPi and SNr with the neuronal retrograde tracer cholera toxin subunit B (CTB), the receptor protein was unmasked and detectable using the antibody. This unmasking of the protein was specific to CTB and not an artifact of the tracer. We have shown unequivocally that the A(2A)R is present in the output nuclei of the primate basal ganglia, however, to be able to detect the receptor immunohistochemically, unmasking the protein with CTB was necessary. The presence of A(2A)Rs in the GPi and SNr suggests that these output nuclei could be targeted therapeutically in Parkinson disease to restore abnormal activity in the basal ganglia.
Neurosciences Division, Center for Applied Medical Research (CIMA), University of Navarra Medical College, Pamplona, Spain.
Natasha
N
Luquin
Salvador
S
Sierra
Alberto J
AJ
Rico
Virginia
V
Gómez-Bautista
Elvira
E
Roda
Lorena
L
Conte-Perales
Rafael
R
Franco
Peter
P
McCormick
José L
JL
Labandeira-García
José L
JL
Lanciego
D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism*; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D003342:Corpus Striatum / Q000166:cytology* / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005917:Globus Pallidus / Q000166:cytology* / Q000378:metabolism; D008252:Macaca fascicularis; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D043683:Receptors, Adenosine A2 / Q000235:genetics / Q000378:metabolism*
D003911:Dextrans; D005904:Glial Fibrillary Acidic Protein; D012333:RNA, Messenger; D043683:Receptors, Adenosine A2; C076397:biotinylated dextran amine; D001710:Biotin; D002772:Cholera Toxin; D002795:Choline O-Acetyltransferase