Excitatory and inhibitory neurons in the CNS are distinguished by several features, including morphology, transmitter content, and synapse architecture [1]. Such distinctions are exemplified in the vertebrate retina. Retinal bipolar cells are polarized glutamatergic neurons receiving direct photoreceptor input, whereas amacrine cells are usually monopolar inhibitory interneurons with synapses almost exclusively in the inner retina [2]. Bipolar but not amacrine cell synapses have presynaptic ribbon-like structures at their transmitter release sites. We identified a monopolar interneuron in the mouse retina that resembles amacrine cells morphologically but is glutamatergic and, unexpectedly, makes ribbon synapses. These glutamatergic monopolar interneurons (GluMIs) do not receive direct photoreceptor input, and their light responses are strongly shaped by both ON and OFF pathway-derived inhibitory input. GluMIs contact and make almost as many synapses as type 2 OFF bipolar cells onto OFF-sustained A-type (AOFF-S) retinal ganglion cells (RGCs). However, GluMIs and type 2 OFF bipolar cells possess functionally distinct light-driven responses and may therefore mediate separate components of the excitatory synaptic input to AOFF-S RGCs. The identification of GluMIs thus unveils a novel cellular component of excitatory circuits in the vertebrate retina, underscoring the complexity in defining cell types even in this well-characterized region of the CNS. Della Santina et al. identify a new neuron type in the mouse retina. These cells (GluMIs) resemble inhibitory interneurons morphologically but make glutamatergic ribbon synapses in the inner retina. GluMIs have light-response features that are distinct from known excitatory interneurons and thus provide a novel pathway for excitation in the retina.

Glutamatergic Monopolar Interneurons Provide a Novel Pathway of Excitation in the Mouse Retina

DELLA SANTINA, LUCA;
2016-01-01

Abstract

Excitatory and inhibitory neurons in the CNS are distinguished by several features, including morphology, transmitter content, and synapse architecture [1]. Such distinctions are exemplified in the vertebrate retina. Retinal bipolar cells are polarized glutamatergic neurons receiving direct photoreceptor input, whereas amacrine cells are usually monopolar inhibitory interneurons with synapses almost exclusively in the inner retina [2]. Bipolar but not amacrine cell synapses have presynaptic ribbon-like structures at their transmitter release sites. We identified a monopolar interneuron in the mouse retina that resembles amacrine cells morphologically but is glutamatergic and, unexpectedly, makes ribbon synapses. These glutamatergic monopolar interneurons (GluMIs) do not receive direct photoreceptor input, and their light responses are strongly shaped by both ON and OFF pathway-derived inhibitory input. GluMIs contact and make almost as many synapses as type 2 OFF bipolar cells onto OFF-sustained A-type (AOFF-S) retinal ganglion cells (RGCs). However, GluMIs and type 2 OFF bipolar cells possess functionally distinct light-driven responses and may therefore mediate separate components of the excitatory synaptic input to AOFF-S RGCs. The identification of GluMIs thus unveils a novel cellular component of excitatory circuits in the vertebrate retina, underscoring the complexity in defining cell types even in this well-characterized region of the CNS. Della Santina et al. identify a new neuron type in the mouse retina. These cells (GluMIs) resemble inhibitory interneurons morphologically but make glutamatergic ribbon synapses in the inner retina. GluMIs have light-response features that are distinct from known excitatory interneurons and thus provide a novel pathway for excitation in the retina.
2016
DELLA SANTINA, Luca; Kuo, Sidney P.; Yoshimatsu, Takeshi; Okawa, Haruhisa; Suzuki, Sachihiro C.; Hoon, Mrinalini; Tsuboyama, Kotaro; Rieke, Fred; Wong, Rachel O. L.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/809926
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