Richard L. Chappell, Professor of Biological Sciences
- BSE, 1962, Princeton University
- Ph.D., 1970, Johns Hopkins University
- Neural Interactions of the Retina
Research efforts are currently focused on the role of zinc in vision and disease. Understanding the effects of zinc on the nervous system and the processing of neural information is a challenging and timely problem. Zinc is the second most abundant trace metal in the body. Its concentration is relatively high in both brain and retina. Reactive zinc (Zn2+) is co-localized with glutamate in a subset of excitatory neurons. Its co-release with glutamate has been demonstrated. It has been suggested that zinc is involved in mechanisms of learning and memory. Already, dietary zinc supplementation is prescribed clinically for a disease affecting the aging retina while benefits of reactive zinc removal have been reported in studies concerning mental loss in the aging brain.
Our studies have found a robust enhancement of the eye’s prominent ON response recorded in an electroretinogram (the ERG b-wave) when extracellular retinal zinc is removed by chelation. The enhancement observed is consistent with the suggestion that zinc, co-released with glutamate at photoreceptor terminals, is involved in feedback which regulates photoreceptor transmitter release. Consistent with this hypothesis, we have demonstrated depolarization-induced zinc release in a retinal slice preparation as well as from individual photoreceptors isolated from the retina. Ongoing studies are designed to investigate mechanisms involved. Knowledge obtained regarding the mechanisms by which zinc functions as a neuromodulator in the retina will provide new insight for understanding the role of zinc in information processing throughout the nervous system.
- Chappell, R.L., I. Anastassov, P. Lugo, and H. Ripps. 2008. Zinc-mediated feedback at the synaptic terminals of vertebrate photoreceptors. Experimental Eye Research.87:394-397
- Redenti, S. and R.L. Chappell. 2007. Müller cell zinc transporter-3 labelling suggests a role in outer retina zinc homeostasis. Molecular Medicine. 13:376-379
- Redenti, S., H. Ripps, and R.L. Chappell. 2007. Zinc release at the synaptic terminals of rod photoreceptors. Experimental Eye Research. 85:580-584
- Qian, H., Y. Zhu, D.J. Ramsey, R.L. Chappell, J.E. Dowling and H. Ripps 2005. Directional asymmetries in the optokinetic response of larval zebrafish (Danio rerio). Zebrafish 2:189-196
- Redenti, S. and R.L. Chappell 2005. Neuroimaging of zinc released by depolarization of rat retinal cells. Vision Res. 45:3520-3525
- Chappell, R.L., H. Qian, J. Zakevicius and H. Ripps 2004. Histidine suppresses zinc modulation of connexin hemichannels. Biological Bulletin 207:188–190
- Redenti, S. and R.L. Chappell 2004. Localization of zinc transporter-3 (ZnT-3) in mouse retina. Vision Research 44:3317–3321
- Qian, H., R.L. Chappell, S. Redenti and H. Ripps 2004. Potassium currents distinguish the two subtypes of morphologically distinct skate bipolar cells. Biological Bulletin 207:191-194