title: Glutamic acid decarboxylase 67 mRNA regulation in two globus pallidus neuron populations by dopamine and the subthalamic nucleus.
abstract: The globus pallidus (GP) consists of two neuron populations, distinguished according to their immunoreactivity for parvalbumin (PV). The PV-immunoreactive (PV+) neurons project preferentially to "downstream" targets such as the subthalamic and entopeduncular nuclei, whereas neurons lacking PV (PV- neurons) project preferentially to the striatum, suggesting a role for PV- cells in feedback to striatal neurons. Although dopamine D2 antagonist administration induces immediate early gene expression preferentially in PV- GP neurons, little is known about long-term regulation of PV- versus PV+ GP neurons. Nigral 6-hydroxydopamine (6-OHDA) lesions or repeated D2-class antagonist injections have been shown to increase pallidal expression of glutamate decarboxylase (GAD(67) isoform) mRNA. This increase in GAD(67) is believed to be secondary to activation of excitatory subthalamopallidal projections. The current study examined the effects of subthalamic nucleus (STN) lesion on 6-OHDA- or repeated D2 antagonist-induced changes in GP GAD(67) mRNA expression in PV+ and PV- neurons. Five or 21 d after nigral 6-OHDA injections or after 3, 7, or 21 d of D2 antagonist administration, GAD(67) mRNA increased in both the PV- and PV+ GP neurons, but the magnitude of the increase was significantly greater in PV- neurons. By contrast, STN lesion resulted in declines in GAD(67) mRNA in both cell populations, with the decreases in PV+ neurons exceeding those in PV- neurons. Furthermore, STN lesion completely blocked 6-OHDA- or D2 antagonist-induced GAD(67) mRNA increases in PV+ cells but only partly offset the GAD(67) mRNA increase in PV- pallidal neurons. Thus, the PV+ and PV- neurons are influenced in qualitatively similar ways by dopamine and the STN, but these cell types exhibit contrasting degrees of regulation by the dopaminergic and STN perturbations. This pattern of results has implications for pallidal control of striatal versus downstream basal ganglia nuclei.
authors.affiliation: Department of Neurobiology and Behavior, University of California, Irvine, California 92627-4550, USA.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Billings
authors.forename: John F
authors.initials: JF
authors.lastname: Marshall
mesh_terms: D000818:Animals; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D005917:Globus Pallidus / Q000166:cytology / Q000378:metabolism*; D005968:Glutamate Decarboxylase / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics*; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D016627:Oxidopamine / Q000494:pharmacology; D010320:Parvalbumins / Q000096:biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013238:Stereotaxic Techniques; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology; D020531:Subthalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis
chemical_list: D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007527:Isoenzymes; D010320:Parvalbumins; D012333:RNA, Messenger; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; D007608:Kainic Acid; D004298:Dopamine