title: Origins of GABA(A) and GABA(B) receptor-mediated responses of globus pallidus induced after stimulation of the putamen in the monkey.
abstract: The external and internal segments of the pallidum (GPe and GPi) receive heavy GABAergic innervations from the neostriatum, an input nucleus of the basal ganglia. The GPe neurons provide another major GABAergic innervation to the GPe itself and GPi. Although these GABAergic inputs are considered to play key roles in controlling the level and pattern of firing activity of pallidal neurons in both normal and pathophysiological conditions, these inputs have not been well characterized in vivo. Here, we characterized the responses of pallidal neurons to single and burst stimulation of the putamen (Put) in awake monkeys. Unit recordings in combination with local infusion of drugs and a chemical blockade of the subthalamic nucleus (STN), the major origin of excitatory afferents, revealed the following. Under STN blockade, the duration of single Put stimulation induced gabazine (a GABA(A) antagonist)-sensitive responses differed greatly in the GPe ( approximately 400 ms long) and in the GPi (60 ms long). Burst stimulation of the Put induced CGP55845 [(2S)-3-[[(1S)-1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl)phosphinic acid] (a GABA(B) antagonist)-sensitive responses in the GPe and GPi. However, the data suggested that the origin of the GABA(B) responses was the GPe, not the Put. Local CGP55845 application increased the spontaneous firing of GPe and GPi neurons, suggesting that GABA released from the axons of GPe neurons effectively activates GABA(B) receptors in the GPe and GPi and contributes significantly to the control of the level of neuronal activity.
authors.affiliation: Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, Tennessee 38163, USA. hkita@utmem.edu
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kita
authors.forename: Satomi
authors.initials: S
authors.lastname: Chiken
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tachibana
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nambu
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D005917:Globus Pallidus / Q000166:cytology*; D008252:Macaca fascicularis; D008253:Macaca mulatta; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010721:Phosphinic Acids / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011699:Putamen / Q000502:physiology* / Q000528:radiation effects; D011724:Pyridazines / Q000494:pharmacology; D018079:Receptors, GABA / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D018755:GABA Agonists; D018756:GABA Antagonists; D010721:Phosphinic Acids; D011412:Propanolamines; D011724:Pyridazines; D018079:Receptors, GABA; C085075:CGP 55845A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C049853:gabazine