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Anatomical and neurochemical characterization of dopaminergic interplexiform processes in mouse and rat retinas
Author(s) -
Witkovsky Paul,
Gábriel Robert,
Križaj David
Publication year - 2008
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21784
Subject(s) - biology , synaptic vesicle , vesicular monoamine transporter 2 , vesicular monoamine transporter , ionotropic effect , dopaminergic , gabaergic , postsynaptic potential , neuroscience , microbiology and biotechnology , neurotransmitter , glutamate receptor , dopamine , dopamine transporter , monoamine neurotransmitter , receptor , inhibitory postsynaptic potential , vesicle , biochemistry , central nervous system , serotonin , membrane
Dopaminergic (DA) neurons of mouse and rat retinas are of the interplexiform subtype (DA‐IPC), i.e., they send processes distally toward the outer retina, exhibiting numerous varicosities along their course. The primary question we addressed was whether distally located DA‐IPC varicosities, identified by tyrosine hydroxylase (TH) immunoreactivity, had the characteristic presynaptic proteins associated with calcium‐dependent vesicular release of neurotransmitter. We found that TH immunoreactive varicosities in the outer retina possessed vesicular monoamine transporter 2 and vesicular GABA transporter, but they lacked immunostaining for any of nine subtypes of voltage‐dependent calcium channel. Immunoreactivity for other channels that may permit calcium influx such as certain ionotropic glutamate receptors and canonical transient receptor potential channels (TRPCs) was similarly absent, although DA‐IPC varicosities did show ryanodine receptor immunoreactivity, indicating the presence of intracellular calcium stores. The synaptic vesicle proteins sv2a and sv2b and certain other proteins associated with the presynaptic membrane were absent from DA‐IPC varicosities, but the vesicular SNARE protein, vamp2, was present in a fraction of those varicosities. We identified a presumed second class of IPC that is GABAergic but not dopaminergic. Outer retinal varicosities of this putative GABAergic IPC did colocalize synaptic vesicle protein 2a, suggesting they possessed a conventional vesicular release mechanism. J. Comp. Neurol. 510:158–174, 2008. © 2008 Wiley‐Liss, Inc.