Lack of evidence for axonal transport of D1 and D2 receptors in the nigro-striatal pathway of the rat.
The possibility that D1 and D2 dopamine receptors are axonally transported in the nigro-striatal pathway has been investigated in the rat by placing a coronal knife cut (sparing the striato-nigral pathway) through the medial forebrain bundle (MFB) and autoradiographically examining the density of D2 (as labeled by [3H]spiperone in the presence of ketanserin) and D1 (as labeled by [3H]SCH 23390) receptors. The efficacy of MFB transection has been assessed by measuring in parallel the binding of [3]ketanserin, a ligand that has been reported to be axonally transported in this bundle. At 12 h post-transection, there was a minor accumulation of [3H]spiperone binding on both sides of the transection. However, (+)butaclamol (1 microM) failed to displace the ligand build-up at the knife cut, thus demonstrating the nonspecific nature of [3H]spiperone accumulation. Similar results were observed at 24, 48, and 72 h after severing the MFB. MFB transection also failed to cause changes in specific [3H]SCH 23390 binding at the knife cut at 12-72 h post-surgery. In contrast, a dramatic accumulation of [3H]ketanserin binding sites was observed rostral and caudal to the cut at 12 h post-transection, attesting to the efficacy of the lesion. These results confirm the existence of both anterograde and retrograde transport of [3H]ketanserin binding sites and suggest that D1 and D2 receptors are not axonally transported in fibers of the nigro-striatal pathway.
Savasta
M
M
Laboratoires d'Etudes et de Recherches Synthélabo (L.E.R.S.), Bagneux, France.
Dubois
A
A
Scatton
B
B
D000818:Animals; D001345:Autoradiography; D001370:Axonal Transport; D003342:Corpus Striatum / Q000378:metabolism*; D008297:Male; D009434:Neural Pathways / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D013378:Substantia Nigra / Q000378:metabolism*
D011954:Receptors, Dopamine