This proposal is to continue studies on Ca2+-mediated synaptic transmitter release from cultured amacrine cells from chicken retina. Conventional patch-clamp techniques together with fluorometric Ca2+-imaging measurements will be used. Four overlapping groups of experiments are planned. The first set of experiments is intended to discover what concentration of cytosolic Ca2+ is required for quantal release of transmitter from amacrine cells. These experiments are designed to test the supposition, based on previous studies that Ca2+ concentrations much lower than generally supposed are sufficient for quantal release. A second set of experiments will test the idea that miniature currents at central synapses are, unlike those at the neuromuscular junction, responses to the simultaneous release of several vesicles, coordinated by local Ca2+ domains. This idea involves eliciting transmitter release in the absence of Ca2+ domains and using Ca2+-imaging to look for the existence of domains. A third set of studies will continue investigations of the mechanisms by which Ca2+ is removed from synapses and transmission is turned off. Outstanding questions in this regard are the stoichiometry of Na+/Ca2+ exchange and the relative importance of mitochondria and endoplasmic reticulum in Ca2+ uptake. Lastly, experiments will investigate the mechanism(s) by which the retinal peptide, neurotensin, found in amacrine cells elicits Ca2+ oscillations and transmitter release.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-VISC (01))
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University of California Davis
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Wilson, Martin; Nacsa, Nick; Hart, Nathan S et al. (2011) Regional distribution of nitrergic neurons in the inner retina of the chicken. Vis Neurosci 28:205-20
Wilson, Martin; Lindstrom, Sarah H (2011) What the bird's brain tells the bird's eye: the function of descending input to the avian retina. Vis Neurosci 28:337-50
Lindstrom, Sarah H; Azizi, Nason; Weller, Cynthia et al. (2010) Retinal input to efferent target amacrine cells in the avian retina. Vis Neurosci 27:103-18
Lindstrom, S H; Nacsa, N; Blankenship, T et al. (2009) Distribution and structure of efferent synapses in the chicken retina. Vis Neurosci 26:215-26
Weller, Cynthia; Lindstrom, Sarah H; De Grip, Willem J et al. (2009) The area centralis in the chicken retina contains efferent target amacrine cells. Vis Neurosci 26:249-54
Borges, Salvador; Lindstrom, Sarah; Walters, Cameron et al. (2008) Discrete influx events refill depleted Ca2+ stores in a chick retinal neuron. J Physiol 586:605-26
Green, Daniel G; Kapousta-Bruneau, Natalia V (2007) Evidence that L-AP5 and D,L-AP4 can preferentially block cone signals in the rat retina. Vis Neurosci 24:9-15
Warrier, Ajithkumar; Wilson, Martin (2007) Endocannabinoid signaling regulates spontaneous transmitter release from embryonic retinal amacrine cells. Vis Neurosci 24:25-35
Warrier, Ajithkumar; Borges, Salvador; Dalcino, David et al. (2005) Calcium from internal stores triggers GABA release from retinal amacrine cells. J Neurophysiol 94:4196-208
Hurtado, Jose; Borges, Salvador; Wilson, Martin (2002) Na(+)-Ca(2+) exchanger controls the gain of the Ca(2+) amplifier in the dendrites of amacrine cells. J Neurophysiol 88:2765-77

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