John Elsworth, PhD

Midbrain dopamine neurons exhibits an exaggerated loss during aging compared with other neuronal populations and consequently, they provide a model system for studying aging mechanisms and repair strategies that is relevant to other CNS neuronal populations.

Specific dysfunction of dopamine neurons is implicated in several neurological and psychiatric disorders, notably Parkinson’s disease and schizophrenia. During the prenatal period the fetal brain undergoes dramatic changes, as structures and connections form according to strict spatial and temporal criteria. It follows then that during development environmental insults have greater potential to exert profound and permanent changes than at other times during life and may affect the risk of the offspring succumbing to CNS disorders. A major focus of investigations is our finding of varying susceptibility of primate dopamine neurons to damage at different periods of development. Our research has identified prenatal phases when primate dopamine neurons are especially vulnerable to oxidative stress or endocrine disruptors and a postnatal period when they are remarkably resistant to such damage. We are particularly intrigued by neuroprotective factors that are preferentially expressed during the window of resistance to damage (‘juvenile protective factors”) and our recent work has focused on paraoxonase-2, a mitochondrial enzyme which if pharmacologically re-activated later in life could preserve and protect neurons vulnerable to age-dependent deficits.

Another field of research is the regulation of dopamine neurons innervating the prefrontal cortex, as our research has indicated that this input appears to determine alteration of dendrites and synapses on prefrontal pyramidal neurons, which are critical to the executive function of this brain region. Experimental restoration of normal dopamine transmission in the prefrontal cortex would enable treatment of cognitive deficits that are characteristic of Parkinson’s disease and schizophrenia.

Other research is focused on repair or maintenance of the vulnerable neuronal system, using strategies such as implants of modified stem cells and neurotrophic factor gene therapy.