John A. Stanford - US grants

Aging is associated with decreased motor function in humans and in animals. Bradykinesia and disturbances of posture and gait have been related to an increased risk of death in the elderly. The similarity of these motor deficits to the symptoms of Parkinson's disease implicates functional changes in the nigrostriatal dopamine (DA) system. These changes, which include a decreased number of DA receptors and diminished evoked DA release and uptake, may contribute to the altered striatal electrophysiological activity that we have recently reported in freely-moving aged Fischer 344 (F344) rats. These electrophysiological alterations may in turn contribute to the progressive deterioration of movement that occurs in aging. Studies conducted in this lab and in others have demonstrated that age-related alterations in movement capacity and DA function can be reversed by the administration of glial cell line-derived neurotrophic factor (GDNF). The purpose of this pilot grant is to determine the effects of GDNF on altered locomotor-related striatal electrophysiological activity in aged (24-month-old) F344 rats. Animals will be behaviorally-characterized with regard to locomotor activity so that relationships between electrophysiology and behavior can be determined. These studies should yield novel and valuable information regarding the physiological basis of GDNF's antiparkinsonian effects.

DESCRIPTION (provided by applicant): In humans and in animals, normal aging is often associated with a marked deterioration in both the quantity and the quality of motor activity. In addition to postural and locomotor deficits, alterations in orolingual and pharyngeal motor function are also associated with human aging. Like locomotor deficits, these disturbances have been found to contribute to an increased risk of death in the elderly. The fact that orolingual motor deficits are also prevalent in Parkinson's disease suggests that alterations in the basal ganglia may play a role in their expression. Although there is considerable evidence linking the basal ganglia to locomotor function, a role for these nuclei in orolingual motor function remains to be examined in animal models of normal aging. The purpose of this grant is to measure orolingual motor function in young, middle-aged and aged animals and to determine relationships between age, behavioral performance and measures of nigrostriatal dopamine (DA) function. In these studies, thirsty rats will be trained to lick water from an isometric force-sensing disc while biophysical and temporal characteristics of tongue movements are measured. A sensorimotor challenge will require rats to extend their tongues increasing distances in order to contact the force-sensing disc. Nigrostriatal DA function will be measured in freely moving animals using intracerebral microdialysis. The effects of antiparkinson drugs will be compared to glial cell line-derived neurotrophic factor (GDNF). These studies should yield novel and valuable information regarding relationships between aging, orolingual motor function and nigrostriatal DA integrity.

[unreadable] DESCRIPTION (provided by applicant): The long-term vision of the principal investigator's (Pl)'s research program involves participating in translational studies of motor control in normal aging and Parkinson's disease (PD). The first step will be to develop clinically-relevant behavioral tests to assess motor control and related neural function in preclinical animal models. While the PI is currently funded to study age-related changes in rats' orolingual motor function, extension of the research program into more sophisticated behavioral and electrophysiological recording techniques is desired. Specifically, the PI needs additional time to work with Dr. Paul D. Cheney, who has agreed to train the PI to perform combined electrophysiological/electromyography (EMG) studies. This will allow the PI to study movement-related neural activity in greater detail and with greater precision. In addition, the PI plans to develop a forelimb force control task into a method to study functional cortical organization and reorganization as a function of age and 6-hydroxydopamine (6-OHDA) depletion in rats. Dr. Randy J. Nudo has agreed to train the PI in sensorimotor cortical mapping techniques so that this procedure can be incorporated into the Pi's laboratory. During the time of the award period, the PI will participate in a graduate-level course in the responsible conduct of scientific research. Dr. James Voogt, former chair of Molecular & Integrative Physiology at the University of Kansas Medical Center, has agreed to serve as a senior faculty mentor to the PI during the award period. Dr. Voogt will counsel the PI on career-related issues and serve as a source of accountability. The K02 award will allow the PI to spend 90% of his time conducting research. It will also provide valuable financial resources since it will allow for 90% of the Pi's salary to be returned to the PI for research-related purposes. [unreadable] [unreadable] Relevance to Public Health: [unreadable] This research should yield information regarding relationships between neural function and motor function in normal aging and in Parkinson's disease. [unreadable] [unreadable] [unreadable]

? DESCRIPTION (provided by applicant): The objective of this proposal is to elucidate the molecular mechanisms that cause denervation of aged neuromuscular junctions (NMJs) and how exercise ameliorates NMJ denervation in aging. In the elderly, progressive denervation of NMJs decreases neuromuscular function, decreases quality of life from frailty, and increases the risk of falling and fractures. However, there are knowledge gaps about the molecular mechanisms that underlie NMJ denervation in aging and how exercise ameliorates this condition. Our long-term goal is to elucidate these mechanisms and to identify new intervention strategies to improve neuromuscular function in the elderly. Here, we hypothesize that an age-related loss of synaptic vesicle release sites - active zones - causes NMJ denervation, and that exercise ameliorates this denervation by restoring active zones at the aged NMJs. This hypothesis has been formulated on the basis of our published and preliminary data that strongly suggest that age-related loss of active zone organizer laminin ?2 causes active zone depletion and NMJ denervation, and that exercise restores active zones and NMJ innervations by increasing laminin ?2 protein expression. Furthermore, these data are firmly supported by our published studies showing the molecular mechanism that organizes NMJ active zones involves interactions between laminin ?2, a specific receptor for laminin ?2 (presynaptic P/Q-type voltage-dependent calcium channels, VDCC), and the active zone protein Bassoon. The specific aims for testing the hypothesis are as follows: (1) Elucidate molecular defects that cause denervation of aged NMJs and how exercise ameliorates the defects. Aged and exercised aged rodents will be analyzed using confocal + super resolution microscopy; (2) Test the hypothesis that exercise maintains aged NMJs by increasing laminin ?2 expression level using transgenic mice; and (3) Evaluate systemic effects of a novel calcium channel agonist on neuromuscular function of aged mice using electrophysiology, electromyography, and behavior tests. This project is innovative because it is based on a novel, untested concept, namely the causality of active zone integrity in NMJ denervation. It is thus distinct from current aging research approaches. Another innovation is the testing of a novel calcium channel agonist specific for the P/Q-type VDCC that was invented by the Co-PI. The significance of this project is that it will yield: (i) the molecular mechanisms of NMJ denervation in aging, (ii) the exercise activated mechanism that ameliorates NMJ denervation in aging, and (iii) a VDCC agonist that may function as an intervention for age-related neuromuscular dysfunction and potentially as an exercise mimetic. Cross-disciplinary investigators from developmental and aging neurobiology, electrophysiology, gerontology, imaging, nephrology, and physiology fields have been assembled for this project.