Director: Thomas Wichmann, M.D.
Title: Udall Parkinson's Disease Center at Emory University: Circuitry to Therapy
Website URL: www.udall.emory.edu
One goal of research of Emory’s Udall Center is to develop a better understanding of how existing surgical and medical treatments for patients with Parkinson’s disease work. While previous studies in this field have largely focused on the effects of these interventions on the activity of neurons in the basal ganglia, i.e., the brain areas that are immediately affected by dopamine loss in Parkinson’s disease, the studies in two of the center’s projects focus on the downstream effects of these interventions, by examining thalamic activities in animals in which basal ganglia output is altered by lesions, stimulation, or other interventions. The thalamus is the anatomical bridge by which basal ganglia output is linked to the cerebral cortex. Abnormalities in the activity of the cerebral cortex directly affect movement, and may lead to the motion abnormalities in Parkinson’s disease. The planned studies will teach us how the basal ganglia output affects thalamic nerve cell activity under normal conditions, and determine the underlying mechanisms by which activity changes in the basal ganglia alter thalamic firing in parkinsonism. The knowledge gained will enable us to devise better therapies that may act to normalize thalamic activities in parkinsonian subjects. By identifying the commonalities and differences between antiparkinsonian interventions that differentially alter basal ganglia output and thalamic activity (lesion or stimulation), we will be able to identify and optimize the thalamic firing patterns associated with successful surgical treatments for the disease.
The second goal of the center’s research is to examine the mechanism of action and therapeutic potential of two non-dopaminergic therapies that provide neuroprotective or symptomatic benefits for Parkinson’s disease. One of the projects examines the symptomatic and neuroprotective effects of a new class of orally administered drugs that act at brain receptors for nerve growth factors. Previous experiments have shown that these drugs may protect dopaminergic neurons from damage in animal models of Parkinson’s disease. The ongoing experiments further explore the use of these drugs in rodent and monkey models of the disease. Another project studies newly developed ‘cholinergic’ drugs in animal models of Parkinson’s disease. Currently available medications in this category have been used to treat Parkinson’s disease for decades, but these agents have many side effects which severely limit their clinical use. Work in Vanderbilt University’s Program in Drug Discovery has recently led to the development of a new group of chemicals that act at cholinergic receptors with much higher specificity than the previously used drugs. The ongoing studies examine the pharmacological and behavioral effects of these drugs in different rodent models of Parkinson’s disease, with the hope of finding drugs that can be used to treat parkinsonism without inducing side effects.
The Udall Center at Emory University examines the pathophysiology of Parkinson’s disease and the mechanisms by which antiparkinsonian treatments work, from a brain circuit perspective, and aims to develop promising lines of non-dopaminergic antiparkinsonian treatments.
Parkinson’s disease is known as a condition in which dopamine loss in the basal ganglia (particularly in the striatum) results
in profound changes in the electrical neuronal activity in the basal ganglia, as well as in brain areas that are linked to
the basal ganglia, specifically the ventrolateral nuclear group in the thalamus. Most of the currently available pharmacological
or surgical treatments were designed to modify or minimize these abnormalities, either by replacing dopamine, or by altering
the influence of basal ganglia output on thalamocortical activity, for instance, by lesioning or stimulation of specific basal
ganglia nuclei. The clinical use of many of these therapies is empiric. Optimization of the use of these treatments is only
possible if their mechanism of action is better understood.
A shortcoming of current attempts to understand the mechanisms of action of existing therapies is that their effects are usually
only considered in terms of the changes they exert on the basal ganglia, while their impact on brain network elements downstream
from the basal ganglia (thalamus and cortex) remains largely unknown. Several of the studies of the Udall Center at Emory
University assess the effects of basal ganglia interventions such as lesions, deep brain stimulation, or pharmacological interventions,
both in rodent and nonhuman primate models of dopamine loss in the basal ganglia. Other projects in this Udall Center aim
to develop new non-dopaminergic drugs as new therapies against parkinsonism, and assess their circuit and cellular effects
in the basal ganglia thalamocortical system.
Through these systems-level studies, the Emory Udall Center brings together researchers from several departments at Emory University and Vanderbilt University with complementary strong expertise in systems-centered Parkinson’s disease research. The center fosters a collaborative, efficient, and productive environment for such research, allowing easy sharing of information and resources. An additional important goal of the center is to educate young researchers and the larger public about Parkinson’s disease research.
The Udall Center at Emory University consists of four research projects (Project 1-4) and two cores (cores A and B). Two
of the research projects examine the impact of parkinsonism and the effects of restorative surgical and pharmacological antiparkinsonian
therapies on the thalamus, the main gateway through which dysfunctional basal ganglia outflow is conveyed to the cerebral
cortex in Parkinson’s disease. Two other projects, including one that is carried out at Vanderbilt University (Project 4)
develop novel non-dopaminergic therapies in Parkinson’s disease.
Project 1 (PI: Dieter Jaeger, PhD) consists of in vivo and brain slice electrophysiologic recording experiments to investigate the impact of basal ganglia output
on thalamic activity, and to assess how abnormal basal ganglia output translates into dysfunctional thalamic activity in parkinsonism.
These studies are carried out in different rodent models, including a model in which dopamine loss in the basal ganglia is
produced by the dopaminergic neurotoxin, MPTP, a mouse model in which chronic progressive parkinsonism is induced by a genetic
modification of VMAT2, one of the molecules involved in dopamine storage and release in the central nervous system, as well
as genetic studies, based on alpha-synuclein overexpression. Project 2 (PI: Thomas Wichmann, MD) explores changes in thalamic activity in parkinsonian primates, and the effects of different neurosurgical interventions
in the basal ganglia on this activity. This project is motivated by the observation that lesions and deep brain stimulation
of the basal ganglia output nuclei have similar clinical antiparkinsonian effects, despite different mechanisms of action
in the basal ganglia. These experiments test the hypothesis that the similar therapeutic effects of these procedures are due
to similarities in their (downstream) effects on thalamic activities. Project 3 (PI: Gary Miller, PhD) examines the efficacy and pharmacokinetic properties of a new group of orally active agonists at TrkB receptors (i.e., the
binding sites mediating neurotrophic activities of brain derived neurotrophic factor [BDNF]) in protecting dopaminergic neurons
and mitigating the signs of parkinsonism in rodent and primate models. Project 4 (PI: P. Jeffery Conn, PhD, Vanderbilt University) is another highly translational project that uses electrophysiological and behavioral studies to examine the involvement
of cholinergic dysfunction in parkinsonism and to test the potential antiparkinsonian efficacy of novel highly subtype-selective
muscarinic receptor agents in rodent models of Parkinson’s disease.
The Center’s administrative core (core A, PI: Thomas Wichmann, MD) coordinates the interactions between the different investigators and their laboratories, is in charge of interactions with the overall Udall Center network, the funding agency, as well as local and external advisors. The core also organizes local meetings, administers the center’s pilot grant program, maintains the center’s website, and organizes the center’s education and outreach activities. The Center’s anatomy and behavior core (core B, PI: Yoland Smith, PhD) conducts the extensive anatomical studies in each project, and primate drug testing studies for Project 3.
Members of the Emory Udall Parkinson’s Disease Center share analysis algorithms, and publish the study data in a timely manner. It is also our policy to make reagents such as the compounds and mouse models used under projects 3 and 4 available (within the limits of patent right restrictions).
In the coming (fourth) year of funding, all of the center’s research projects will continue to pursue their original goals. Under project 1, brain slice recordings and in vivo studies will be carried out to study the impact of the activity of substantia nigra neurons on thalamic activities, with a focus on genetic models of Parkinson’s disease. Under project 2, additional animals will be added to the different study groups, and specific emphasis will be placed on completing the analysis of the data gathered thus far. Project 3 personnel will continue to study TrkB agonist effects on parkinsonism in MPTP-treated and VMAT2LO mice, and will focus on a better definition of the precise location(s) of action of these agents. In project 4, muscarinic M1 receptor and muscarinic M4 receptor ligands will be tested in brain lice recording studies, and in in vivo experiments in parkinsonian rodents. Core B continues to support the projects with anatomic studies, helping with a variety of tasks, including the reconstruction of electrode tracks, as well as light- and electron microscopic immunochemical studies of the anatomy of the basal ganglia and thalamus experiments. A specific emphasis will be on the study of thalamic changes in animals with pallidal lesions. Core A will continue to help with administrative tasks, organize the pilot project program, and interact with the public.
Center support has contributed to 24 publications this year. A sample of these includes:
Parkinsonism-related features of neuronal discharge in primates.
Sanders TH, Clements MA, Wichmann T. J Neurophysiol. 2013 Aug;110(3):720-31. PMID:
GABAergic inputs from direct and indirect striatal projection neurons onto cholinergic interneurons in the primate putamen.
Gonzales KK, Pare JF, Wichmann T, Smith Y. J Comp Neurol. 2013 Aug 1;521(11):2502-22.
More than meets the Eye-Myelinated axons crowd the subthalamic nucleus.
Mathai A, Wichmann T, Smith Y. Mov Disord. 2013 Jul 12. PMID: 23852565
Last updated October 31, 2013