Synaptic Vesicle Exocytosis at the Dendritic Lobules of an Inhibitory Interneuron in the Mammalian Retina.
- Author(s): Balakrishnan, Veeramuthu
- Puthussery, Theresa
- Kim, Mean-Hwan
- Taylor, W Rowland
- von Gersdorff, Henrique
- et al.
Published Web Locationhttps://www.cell.com/neuron/pdfExtended/S0896-6273(15)00638-8
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.