Spontaneous IPSCs and glycine receptors with slow kinetics in wide-field amacrine cells in the mature rat retina

• Published in: The Journal of physiology 2007-05, Vol.581 (1), p.203-219
• Main Authors: Veruki, Margaret Lin, Gill, Silje Bakken, Hartveit, Espen
• Format: Article
• Language: English
• Subjects: Amacrine Cells - cytology; Amacrine Cells - physiology; Animals; Electrophysiology; Glycine Agents - pharmacology; Inhibitory Postsynaptic Potentials - drug effects; Inhibitory Postsynaptic Potentials - physiology; Ion Channel Gating - physiology; Kinetics; Neuroscience; Patch-Clamp Techniques; Rats; Rats, Mutant Strains; Receptors, Glycine - physiology; Retina - cytology; Retina - physiology; Strychnine - pharmacology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2006.127316

The functional properties of glycine receptors were analysed in different types of wide-field amacrine cells, narrowly stratifying cells considered to play a role in larger-scale integration across the retina. The patch-clamp technique was used to record spontaneous IPSCs (spIPSCs) and glycine-evoked patch responses from mature rat retinal slices (4–7 weeks postnatal). Glycinergic spIPSCs were blocked reversibly by strychnine (300 n m ). Compared to previously described spIPSCs in AII amacrine cells, the spIPSCs in wide-field amacrine cells displayed a very slow decay time course (τ fast ∼ 15 ms; τ slow ∼ 57 ms). The kinetic properties of spIPSCs in whole-cell recordings were paralleled by even slower deactivation kinetics of responses evoked by brief pulses of glycine (3 m m ) to outside-out patches from wide-field amacrine cells (τ fast ∼ 45 ms; τ slow ∼ 350 ms). Non-stationary noise analysis of patch responses and spIPSCs yielded similar average single-channel conductances (∼31 and ∼34 pS, respectively). Similar, as well as both lower- and higher-conductance levels could be identified from directly observed single-channel gating during the decay phase of spIPSCs and patch responses. These results suggest that the slow glycinergic spIPSCs in wide-field amacrine cells involve α2β heteromeric receptors. Taken together with previous work, the kinetic properties of glycine receptors in different types of amacrine cells display a considerable range that is probably a direct consequence of differential expression of receptor subunits. Unique kinetic properties are likely to differentially shape the glycinergic input to different types of amacrine cells and thereby contribute to distinct integrative properties among these cells.