Abstract
We have investigated the uptake and release of [3H]gamma-aminobutyric acid (GABA) by embryonic chick spinal cord cells maintained in culture. Cells dissociated from 4- or 7-d-old embryos were studied between 1 and 3 wk after plating. At 3 degrees C, [3H]GABA was accumulated by a high affinity (Km approximately equal to 4 microM) and a low affinity (Km approximately equal to 100 microM) mechanism. The high affinity transport was markedly inhibited in low Na+ media, by ouabain, at 0 degrees C, and by 2,4-diaminobutyric acid. Autoradiography, after incubation in 0.1 microM [3H]GABA, showed that approximately 50% (range = 30-70%) of the multipolar cells were labeled. These cells were neurons rather than glia; action potentials and/or synaptic potentials were recorded in cells subsequently found to be labeled. Non-neuronal, fibroblast-like cells and co-cultured myotubes were not labeled under the same conditions. The fact that not all of the neurons were labeled is consistent with the suggestion, based on studies of intact adult tissue, that high affinity transport of [3H]GABA may be unique to neurons that use GABA as a neurotransmitter. Our finding that none of fifteen physiologically identified cholinergic neurons, i.e., cells that innervated nearby myotubes, were heavily labeled after incubation in 0.1 microM [3H]GABA is significant in this regard. The newly taken up [3H]GABA was not metabolized in the short run. It was stored in a form that could be released when the neurons were depolarized in a high K+ (100 mM) medium. As expected for a neurotransmitter, the K+-evoked release was reversibly inhibited by reducing the extracellular Ca++/Mg++ ratio.
Full Text
The Full Text of this article is available as a PDF (2.7 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Barker J. L., Nicoll R. A. The pharmacology and ionic dependency of amino acid responses in the frog spinal cord. J Physiol. 1973 Jan;228(2):259–277. doi: 10.1113/jphysiol.1973.sp010085. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Iversen L. L., Bloom F. E. Studies of the uptake of 3 H-gaba and ( 3 H)glycine in slices and homogenates of rat brain and spinal cord by electron microscopic autoradiography. Brain Res. 1972 Jun 8;41(1):131–143. doi: 10.1016/0006-8993(72)90621-x. [DOI] [PubMed] [Google Scholar]
- Kellerth J. O., Szumski A. J. Effects of picrotoxin on stretch-activated post-synaptic inhibitions in spinal motoneurones. Acta Physiol Scand. 1966 Jan-Feb;66(1):146–156. doi: 10.1111/j.1748-1716.1966.tb03179.x. [DOI] [PubMed] [Google Scholar]
- McLaughlin B. J., Barber R., Saito K., Roberts E., Wu J. Y. Immunocytochemical localization of glutamate decarboxylase in rat spinal cord. J Comp Neurol. 1975 Dec 1;164(3):305–321. doi: 10.1002/cne.901640304. [DOI] [PubMed] [Google Scholar]
- Miyata Y., Otsuka M. Distribution of -aminobutyric acid in cat spinal cord and the alteration produced by local ischaemia. J Neurochem. 1972 Jul;19(7):1833–1834. doi: 10.1111/j.1471-4159.1972.tb06233.x. [DOI] [PubMed] [Google Scholar]
- Obata K., Ito M., Ochi R., Sato N. Pharmacological properties of the postsynaptic inhibition by Purkinje cell axons and the action of gamma-aminobutyric acid on deiters NEURONES. Exp Brain Res. 1967;4(1):43–57. doi: 10.1007/BF00235216. [DOI] [PubMed] [Google Scholar]
- Otsuka M., Obata K., Miyata Y., Tanaka Y. Measurement of gamma-aminobutyric acid in isolated nerve cells of cat central nervous system. J Neurochem. 1971 Feb;18(2):287–295. doi: 10.1111/j.1471-4159.1971.tb00567.x. [DOI] [PubMed] [Google Scholar]
- Peacock J. H., Nelson P. G., Goldstone M. W. Electrophysiologic study of cultured neurons dissociated from spinal cords and dorsal root ganglia of fetal mice. Dev Biol. 1973 Jan;30(1):137–152. doi: 10.1016/0012-1606(73)90053-5. [DOI] [PubMed] [Google Scholar]
- Tunnicliff G., Cho Y. D., Blackwell N., Martin R. O., Wood J. D. The uptake of gamma-aminobutyrate by organotypic cultures of chick spinal cord. Biochem J. 1973 May;134(1):27–32. doi: 10.1042/bj1340027. [DOI] [PMC free article] [PubMed] [Google Scholar]