title: Pallidal neuronal discharge in Parkinson's disease following intraputamenal fetal mesencephalic allograft.
abstract: BACKGROUND
  Human intrastriatal fetal allografts survive over long periods of time in the brains of Parkinson's disease (PD) patients and integrate into host circuitry. However, some grafted patients with a prior history of levodopa-induced dyskinesias have developed off-medication dyskinesias and dystonias following allografting whose mechanism remains poorly understood. The authors present single-unit discharge characteristics in the external and internal globus pallidus (GPe and GPi) in an awake patient with PD undergoing microelectrode-guided surgery for pallidal deep brain stimulation, 10 years following bilateral intraputamenal fetal mesencephalic allografting in an NIH-funded protocol.
  
  
  METHODS
  Pallidal single-unit activity at 'rest' and during active movement was evaluated and compared with data sets from 13 PD patients in the 'off-medication' state and from one non-dyskinetic PD patient in the 'on-medication' state.
  
  
  CONCLUSIONS
  Analysis of firing rate, bursting discharge and oscillatory activity showed that the graft corrected some, but not all, of the abnormalities associated with the off-medication state. Additionally, in the transplanted patient, voluntary hand movement produced a marked reduction in pallidal discharge rate at multiple GPi recording sites, which was not observed during active movement in other patients. These findings are consistent with a persistent effect of transplanted dopamine cells on basal ganglia outflow and suggest a mechanism for the graft-induced dystonic phenotype.
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Avenue, Box 0112, San Francisco, CA 94143, USA. richardsonma@neurosurg.ucsf.edu
authors.forename: R Mark
authors.initials: RM
authors.lastname: Richardson
authors.forename: Curt R
authors.initials: CR
authors.lastname: Freed
authors.forename: Shoichi A
authors.initials: SA
authors.lastname: Shimamoto
authors.forename: Philip A
authors.initials: PA
authors.lastname: Starr
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D016380:Brain Tissue Transplantation; D046690:Deep Brain Stimulation; D016332:Fetal Tissue Transplantation; D005917:Globus Pallidus / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D009474:Neurons / Q000502:physiology; D010300:Parkinson Disease / Q000503:physiopathology / Q000601:surgery*; D049268:Positron-Emission Tomography; D011699:Putamen / Q000196:embryology / Q000637:transplantation