Switching between transient and sustained signalling at the rod bipolar-AII amacrine cell synapse of the mouse retina

Josefin Snellman, David Zenisek, Scott Nawy

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

At conventional synapses, invasion of an action potential into the presynaptic terminal produces a rapid Ca2+ influx and ultimately the release of synaptic vesicles. However, retinal rod bipolar cells (RBCs) generally do not produce action potentials, and the rate of depolarization of the axon terminal is instead governed by the rate of rise of the light response, which can be quite slow. Using paired whole-cell recordings, we measured the behaviour of the RBC-AII amacrine cell synapse while simulating light-induced depolarizations either by slowly ramping the RBC voltage or by depolarizing the RBC with the mGluR6 receptor antagonist (R,S)-α-cyclopropyl-4- phosphonophenylglycine (CPPG). Both voltage ramps and CPPG evoked slow activation of presynaptic Ca2+ currents and severely attenuated the early, transient component of the AII EPSC compared with voltage steps. We also found that the duration of the transient component was limited in time, and this limitation could not be explained by vesicle depletion, inhibitory feedback, or proton inhibition. Limiting the duration of the fast transient insures the availability of readily releasable vesicles to support a second, sustained component of release. The mGluR6 pathway modulator cGMP sped the rate of RBC depolarization in response to puffs of CPPG and consequently potentiated the transient component of the EPSC at the expense of the sustained component. We conclude that the rod bipolar cell is capable of both transient and sustained signalling, and modulation of the mGluR6 pathway by cGMP allows the RBC to switch between these two time courses of transmitter release.

Original languageEnglish (US)
Pages (from-to)2443-2455
Number of pages13
JournalJournal of Physiology
Volume587
Issue number11
DOIs
StatePublished - Jun 11 2009

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Amacrine Cells
Synapses
Retina
Presynaptic Terminals
Action Potentials
Retinal Bipolar Cells
Retinal Rod Photoreceptor Cells
Light
Architectural Accessibility
Synaptic Vesicles
Patch-Clamp Techniques
Protons
cyclopropyl-4-phosphonophenylglycine
metabotropic glutamate receptor 6

ASJC Scopus subject areas

  • Physiology

Cite this

Switching between transient and sustained signalling at the rod bipolar-AII amacrine cell synapse of the mouse retina. / Snellman, Josefin; Zenisek, David; Nawy, Scott.

In: Journal of Physiology, Vol. 587, No. 11, 11.06.2009, p. 2443-2455.

Research output: Contribution to journalArticle

Snellman, Josefin ; Zenisek, David ; Nawy, Scott. / Switching between transient and sustained signalling at the rod bipolar-AII amacrine cell synapse of the mouse retina. In: Journal of Physiology. 2009 ; Vol. 587, No. 11. pp. 2443-2455.
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