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Glycinergic neurons in the human retina
Author(s) -
Frederick Jeanne M.,
Rayborn Mary E.,
Hollyfield Joe G.
Publication year - 1984
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.902270203
Subject(s) - inner plexiform layer , retina , inner nuclear layer , glycine receptor , glycine , outer plexiform layer , population , biophysics , neurotransmitter , retinal , postsynaptic potential , ribbon synapse , biology , inhibitory postsynaptic potential , depolarization , neuroscience , anatomy , chemistry , biochemistry , amino acid , synaptic vesicle , central nervous system , receptor , medicine , vesicle , environmental health , membrane
Neurotransmitter‐specific properties of glycinergic neurons in the human retina were studied using 11 pairs of eyes from donors ranging from 2 1/2 to 54 years in age. A mean endogenous level of 10.3 nmoles glycine per mg protein was measured by amino acid analysis in retinas isolated within 1 hour postmortem. When retinas were incubated with 3 H‐glycine (2 μM) and processed for autoradiography, label was found associated with neurons whose somata reside within the inner nuclear layer. Some heavily labeled neurons located at the vitread border of the inner nuclear layer were identified as amacrine cells based on ultrastructural verification of the conventional synaptic contacts made by their processes in distal regions of the inner plexiform layer. In proximal regions of the inner plexiform layer, dendrites of glycine‐accumulating amacrine cells were postsynaptic to both ribbon and conventional synaptic contacts, suggesting input from bipolar and other, nonglycinergic amacrine cells. Their density (30 ± 11 S.D. cells/mm linear retinal expanse) tended to be greater toward the central fundus. A second population of lightly labeled, probable bipolar cells was present in the middle of the inner nuclear layer; the density of this second set of glycine‐accumulating cells approximated that of the heavily labeled population from the fovea, centrally, to the ora serrata, peripherally. Release of either accumulated or endogenous glycine was elicited by K + ‐depolarization in a Ca 2+ ‐dependent manner. Tissue fragments exposed for 6 minutes to normal medium, 40 mM K + ‐substituted medium, or K + ‐substituted medium with Co 2+ release endogenous glycine into each bathing solution in average amounts of 0.6, 2.6, and 0.7 nmoles per mg protein, respectively. Together these data strongly implicate glycine as a neurotransmitter in the human retina.