title: Does heterogeneity of intracellular Ca[Formula: see text] dynamics underlie speed tuning of direction-selective responses in starburst amacrine cells?
abstract: The starburst amacrine cell (SAC) plays a fundamental role in retinal motion perception. In the vertebrate retina, SAC dendrites have been shown to be directionally selective in terms of their Ca[Formula: see text] responses for stimuli that move centrifugally from the soma. The mechanism by which SACs show Ca[Formula: see text] bias for centrifugal motion is yet to be determined with precision. Recent morphological studies support a presynaptic delay in glutamate receptor activation induced Ca[Formula: see text] release from bipolar cells preferentially contacting SACs. However, bipolar cells are known to be electrotonically coupled so time delays between the bipolar cells that provide input to SACs seem unlikely. Using fluorescent microscopy and imunnostaining, we found that the endoplasmic reticulum (ER) is omnipresent in the soma extending to the distal processes of SACs. Consequently, a working hypothesis on heterogeneity of intracellular Ca[Formula: see text] dynamics from ER is proposed as a possible explanation for the cause of speed tuning of direction-selective Ca[Formula: see text] responses in dendrites of SACs.
authors.affiliation: * National Institutes of Natural Sciences 105-0001, Tokyo, Japan.|† National Institute for Physiological Sciences Okazaki, Aichi 444-8585, Japan.
authors.forename: Amane
authors.initials: A
authors.lastname: Koizumi
authors.affiliation: ‡ Department of Clinical Sciences Faculty of Biosciences and Medical Engineering Universiti Teknologi Malaysia 81310 Johor Bahru, Malaysia.
authors.forename: Roman R
authors.initials: RR
authors.lastname: Poznanski
keywords: Calcium ions; ChAT-immunostaining; Endoplasmic reticulum; bipolar cells. CICR mechanism; calcium tunneling model; direction-selectivity; fluorescent imaging; organotypic cultured mammalian retina; starburst amacrine cells