title: Synaptic Vesicle Exocytosis at the Dendritic Lobules of an Inhibitory Interneuron in the Mammalian Retina.
abstract: Ribbon synapses convey sustained and phasic excitatory drive within retinal microcircuits. However, the properties of retinal inhibitory synapses are less well known. AII-amacrine cells are interneurons in the retina that exhibit large glycinergic synapses at their dendritic lobular appendages. Using membrane capacitance measurements, we observe robust exocytosis elicited by the opening of L-type Ca(2+) channels located on the lobular appendages. Two pools of synaptic vesicles were detected: a small, rapidly releasable pool and a larger and more slowly releasable pool. Depending on the stimulus, either paired-pulse depression or facilitation could be elicited. During early postnatal maturation, the coupling of the exocytosis Ca(2+)-sensor to Ca(2+) channel becomes tighter. Light-evoked depolarizations of the AII-amacrine cell elicited exocytosis that was graded to light intensity. Our results suggest that AII-amacrine cell synapses are capable of providing both phasic and sustained inhibitory input to their postsynaptic partners without the benefit of synaptic ribbons.
authors.affiliation: The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Veeramuthu
authors.initials: V
authors.lastname: Balakrishnan
authors.affiliation: Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Puthussery
authors.affiliation: The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Mean-Hwan
authors.initials: MH
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: W Rowland
authors.initials: WR
authors.lastname: Taylor
authors.affiliation: The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA. Electronic address: vongersd@ohsu.edu.
authors.forename: Henrique
authors.initials: H
authors.lastname: von Gersdorff
mesh_terms: D025042:Amacrine Cells / Q000378:metabolism; D000818:Animals; D005089:Exocytosis / Q000502:physiology*; D007395:Interneurons / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009433:Neural Inhibition / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011817:Rabbits; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000378:metabolism*