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Postnatal development of GABA‐ergic neurons in the rabbit retina
Author(s) -
ManKit Lam Dominic,
Fung SekChung,
Kong YunCheung
Publication year - 1980
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.901930107
Subject(s) - glutamate decarboxylase , retina , biology , gaba transaminase , glutamate receptor , gamma aminobutyric acid , neurotransmitter , retinal , neuroscience , extracellular , amacrine cell , gabaergic , medicine , microbiology and biotechnology , endocrinology , biochemistry , central nervous system , enzyme , inhibitory postsynaptic potential , receptor
Uptake, synthesis, storage, and release of γ‐aminobutyric acid (GABA) are some of the characteristic properties of GABA‐ergic neurons. In the present study, we have used these properties as physiological probes to follow the emergence and maturation of GABA‐ergic neurons during postnatal development of the rabbit retina. There is autoradiographic, immunocytochemical, and pharmacological evidence that some amacrine cells and certain neurons in the ganglion cell layer probably use GABA as the neurotransmitter. These neurons take up GABA, contain the GABA‐synthesizing enzyme L‐glutamic acid decarboxylase (GAD, EC 4.1.1.15), and release the accumulated GABA by a Ca ++ ‐dependent mechanism when depolorized with high extracellular K + concentration. In this study, we show that certain neurons in the newborn retina already possess a specific mechanism for GABA uptake. The positions and numbers of these cells in the developing retina suggest that they will become GABA‐ergic neurons in the adultretina. These putative GABA‐ergic neurons are, however, probably immature an birth because newborn retinas contain only low levels of GABA and GAD. Additionally, there is relatively little K + ‐stimulated, Ca ++ ‐dependent release of ( 3 H)‐GABA from the newborn retinas. GABA concentrations and GAD activities in developing retinas increase steadily postnatally, reaching about 80% of the adult levels by day 9. The activities of the GABA‐degrading enzyme, GABA‐glutamate transaminase (GABA‐T, EC 2.6.1.19), follow a similar pattern of maturation during retinal development. K + stimulated GABA release, however, remains low until about day 6, and then increases dramatically from 20% to 85% of the adult level over the next 3 days. Taken together, our results indicate that in the rabbit retina, the commitment by certain neurons to use GABA as the transmitter is made prenatally. These neurons are immature at birth but are biochemically, physiologically, and probably functionally mature by about 9 days after birth.