Responses to Light of Starburst Amacrine Cells. Peters, Bruce N., Richard H. Masland. Program in Neuroscience, Harvard Medical School and Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Ma. 02114 USA, Tel: (617) - 726-6927.
APStracts 2:0251N, 1995.
SUMMARY AND CONCLUSIONS
1. Starburst amacrine cells were studied using whole cell patch recording. Displaced starburst cells were labeled in rabbit retinas by intraocular injection of DAPI. The retinas were isolated and maintained in vitro. The inner limiting membrane and M[umlaut]uller cell endfeet were mechanically removed from small areas above the starburst cell bodies, allowing an unimpeded approach under visual control to the cells. A total of 104 cells was studied. 2. In voltage clamp recordings, the cells responded to light with slow, graded inward and outward currents on which were superimposed smaller, rapid inward currents. The rapid inward currents appeared to be post-synaptic currents. 3. The receptive fields of the cells were mapped using small spots. They had an ON center, OFF surround organization. Visualizing the dendrites by including Lucifer Yellow in the patch pipette showed that the receptive fields' centers closely approximated the dendritic spread of the neurons. 4. The cells' responses to movement were tested with smooth movements or with two-spot apparent motion. No directional preference was seen for spots swept across the whole receptive field, for centrifugal movements, or for centripetal movements. 5. Bath-applied TTX or intracellularly applied QX-314 had no effect on any component of the spontaneous or light-evoked activity. Depolarization of the cell bodies by injected current showed evidence of active conductances, but they were unaffected by TTX or QX-314. 6. CNQX eliminated the small rapid currents, indicating that they depend on AMPA/kainate glutamate receptors. 7. Because it is unlikely that we voltage clamped the distalmost dendrites of these wide-field cells, uncertainties remain about rapid electrical events occurring in the dendrites. From a functional point of view, though, the fact that slow responses to distal photic stimulation were recorded at the soma suggests that the starburst cells could in principle integrate inputs across fairly substantial fractions of their total dendritic arbors. The extent to which this actually occurs remains to be learned. 

Received 4 April 1995; accepted in final form 14 August 1995.
APS Manuscript Number J224-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.