Journal of Neurophysiology, Vol 69, Issue 2 352-360, Copyright © 1993 by APS

ARTICLES

Properties of synaptic transmission from photoreceptors to bipolar cells in the mudpuppy retina

H. G. Kim and R. F. Miller
Department of Physiology, University of Minnesota, Minneapolis 55455.

1. Simultaneous, whole-cell recordings were obtained from synaptically coupled photoreceptor/bipolar cell pairs, by the use of direct visualization in a superfused, mudpuppy retinal slice preparation. 2. OFF-bipolar cells (BPs) generated sign-conserving responses when extrinsic current was injected into rods and cones, whereas ON-BPs generated a sign-reversing response. OFF-BPs (n = 24) responded faster than ON-BPs (n = 12), in terms of response latency (27.8 vs. 80.6 ms) and peak response times (50.5 vs. 159.8 ms) when current was injected into photoreceptors. We did not detect any significant difference between rod- versus cone-mediated latency or peak response times in the ON- and OFF-BP subtypes. 3. Rod and cone inputs to OFF-BPs were blocked by kynurenic acid (Kyn), but the doses required were significantly higher for rod inputs: the IC50 (the concentration at which an antagonist blocks 50% of the responses) for Kyn was 0.3 mM for cone inputs and 1 mM for rod inputs. 4. Rod inputs to OFF-BPs showed the same Kyn sensitivity as rod inputs to horizontal cells (HCs). However, cone inputs to HCs (IC50 < 200 microM) were more sensitive to Kyn than those to OFF-BPs. 5. The pharmacological studies presented here, together with previous studies, suggest that the sign-conserving pathway in the outer plexiform layer of the mudpuppy retina involves at least three subtypes of glutamate receptors: 1) cone-activated receptors of HCs; 2) cone-activated receptors of OFF-BPs; and 3) rod-activated receptors found in HCs and BPs.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				L. Cadetti, D. Tranchina, and W. B. Thoreson A comparison of release kinetics and glutamate receptor properties in shaping rod-cone differences in EPSC kinetics in the salamander retina J. Physiol., December 15, 2005; 569(3): 773 - 788. [Abstract] [Full Text] [PDF]

				C. E. Armstrong-Gold and F. Rieke Bandpass Filtering at the Rod to Second-Order Cell Synapse in Salamander (Ambystoma tigrinum) Retina J. Neurosci., May 1, 2003; 23(9): 3796 - 3806. [Abstract] [Full Text] [PDF]

				D. A. Burkhardt and P. K. Fahey Contrast Rectification and Distributed Encoding By ON-OFF Amacrine Cells in the Retina J Neurophysiol, October 1, 1999; 82(4): 1676 - 1688. [Abstract] [Full Text] [PDF]

				D. A. Burkhardt and P. K. Fahey Contrast Enhancement and Distributed Encoding by Bipolar Cells in the Retina J Neurophysiol, September 1, 1998; 80(3): 1070 - 1081. [Abstract] [Full Text] [PDF]

				T. Euler, H. Schneider, and H. Wassle Glutamate Responses of Bipolar Cells in a Slice Preparation of the Rat Retina J. Neurosci., May 1, 1996; 16(9): 2934 - 2944. [Abstract] [Full Text] [PDF]