The objective of this research project is to understand how the retina of mammals analyzes the visual world and encodes its spatial, temporal and chromatic contrast into a message of action potentials for safe sending to the brain. It is proposed to investigate which chemical messages are converging upon each type of retinal neuron, the weight of these messages, their destination at the cell surface and their neuron of origin. Furthermore, if one were able to recognize in vitro, after retinal dissociation, the neuron that represents the target of such messenger molecules, one could correlate its wiring with the cell's physiology. One would also possess a strategy for designing critical physiological experiments and investigate the influence of the appropriate constellation of neuroactive substances on the ligand- and voltage-gated currents of the postsynaptic cell. Armed with this combined knowledge of structure and function, if one could identify morphologically the various species of receptors and ion channels expressed by each type of retinal neuron, one could perhaps predict the nature of the neural interactions at sites that are not accessible to physiological experimentation.
Aim of this application, in addition to that of completing ongoing work on the bipolar cells of the rabbit, is to combine molecular biology with microscopy and electrophysiology in the study of the functional wiring of the mouse retina. Homogeneous populations of retinal neurons will be labeled by introducing into the mouse genome chimeric constructs consisting of a reporter gene and the promoters of genes whose products participate in visual processing. The reporter genes are (i) alkaline phosphatase that can be detected at both light and electron microscopes with simple and reliable techniques; (ii) beta-galactosidase that can be identified in living cells with a fluorescent dye. The promoters will be those that regulate transcription of genes coding for peptides, rate-limiting enzymes of transmitter metabolism, receptors and ion channels. The morphological parameters of the labeled cell populations will be studied as well as their synaptic connections. Furthermore, living cells that carry the reporter gene will be identified in vitro after dissociation of the retina: in this way, it will be possible to study the voltage- and ligand-gated currents of the retinal neurons that carry the transgene by means of the whole-cell patch clamp technique and integrate the data thus obtained into the neural networks that were described anatomically. These sort of studies are fundamental to the understanding and rational treatment of the disorders of the retina and nervous system in general.
| Hirasawa, Hajime; Contini, Massimo; Raviola, Elio (2015) Extrasynaptic release of GABA and dopamine by retinal dopaminergic neurons. Philos Trans R Soc Lond B Biol Sci 370: |
| Hirasawa, Hajime; Betensky, Rebecca A; Raviola, Elio (2012) Corelease of dopamine and GABA by a retinal dopaminergic neuron. J Neurosci 32:13281-91 |
| Contini, Massimo; Lin, Bin; Kobayashi, Kazuto et al. (2010) Synaptic input of ON-bipolar cells onto the dopaminergic neurons of the mouse retina. J Comp Neurol 518:2035-50 |
| Hirasawa, Hajime; Puopolo, Michelino; Raviola, Elio (2009) Extrasynaptic release of GABA by retinal dopaminergic neurons. J Neurophysiol 102:146-58 |
| Dorenbos, Ronald; Contini, Massimo; Hirasawa, Hajime et al. (2007) Expression of circadian clock genes in retinal dopaminergic cells. Vis Neurosci 24:573-80 |
| Storch, K-F; Paz, C; Signorovitch, J et al. (2007) Physiological importance of a circadian clock outside the suprachiasmatic nucleus. Cold Spring Harb Symp Quant Biol 72:307-18 |
| Puopolo, Michelino; Raviola, Elio; Bean, Bruce P (2007) Roles of subthreshold calcium current and sodium current in spontaneous firing of mouse midbrain dopamine neurons. J Neurosci 27:645-56 |
| Puopolo, Michelino; Bean, Bruce P; Raviola, Elio (2005) Spontaneous activity of isolated dopaminergic periglomerular cells of the main olfactory bulb. J Neurophysiol 94:3618-27 |
| MacNeil, Margaret A; Heussy, John K; Dacheux, Ramon F et al. (2004) The population of bipolar cells in the rabbit retina. J Comp Neurol 472:73-86 |
| Gustincich, Stefano; Contini, Massimo; Gariboldi, Manuela et al. (2004) Gene discovery in genetically labeled single dopaminergic neurons of the retina. Proc Natl Acad Sci U S A 101:5069-74 |
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