Pallidal border cells: An anatomical and electrophysiological study in the1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkey

A dopamine transporter-radioligand binding study demonstrated a dopaminergi c innervation around the pallidal complex in the normal monkey (n = 5), i.e . where a subpopulation of pallidal neurons known as "border cells" is clas sically identified. Surprisingly, this peripallidal binding persists in mon keys rendered parkinsonian (n = 5) with 1-methyl-4-phenyl-1,2,3,6-tetrahydr opyridine treatment. The border cell electrophysiological activity was then analysed in normal and parkinsonian monkeys (n = 2), either in the untreat ed state or following administration of levodopa. Pallidal border cell firi ng frequency was significantly decreased after 1-methyl-4-phenyl-1,2,3,6-te trahydropyridine treatment (8.9 +/- 0.7 vs 31.4 +/- 1.6 Hz, P < 0.05). This decrease was partly corrected by levodopa administration (19.2 +/- 1.0 Hz, P < 0.05 vs both normal and parkinsonian situations). The peripallidal dopaminergic innervation suggests that pallidal border cel ls are under a direct dopaminergic control, arising from the ventral tegmen tal area and/or the basal forebrain magnocellular complex, the role of whic h remains unknown. Moreover, the relative sparing of these dopaminergic fib ers in parkinsonian monkeys suggests that they would exhibit specific adapt ive properties totally different from those described in the nigrostriatal pathway. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reser ved.