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Sodium‐Dependent Proline Uptake in the Rat Hippocampal Formation: Association with Ipsilateral‐Commissural Projections of CA3 Pyramidal
Author(s) -
Nadler Cells J. Victor
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb10006.x
Subject(s) - fascia dentata , proline , hippocampal formation , kainic acid , chemistry , glutamate receptor , biophysics , glycine , amino acid , biochemistry , biology , medicine , endocrinology , receptor , dentate gyrus
Na + ‐dependent uptake of L‐[ 3 H]proline was measured in a crude synaptosomal preparation from the entire rat hippocampal formation or from isolated hippo‐campal regions. Among hippocampal regions, Na + ‐depen‐dent proline uptake was significantly greater in areas CA1 and CA2‐CA3‐CA4 than in the fascia dentata, whereas there was no marked regional difference in the distribution of Na + ‐dependent γ‐[ 14 C]aminobutyric acid ([ 14 C] GABA) uptake. A bilateral kainic acid lesion, which destroyed most of the CA3 hippocampal pyramidal cells, reduced Na + ‐de‐pendent proline uptake by an average of 41% in area CA1 and 52% in area CA2‐CA3‐CA4, without affecting the Na + ‐dependent uptake of GABA. In the fascia dentata, neither proline nor GABA uptake was significantly altered. Kinetic studies suggested that hippocampal synaptosomes take up proline by both a high‐affinity ( K T =6.7 μ M ) and a low‐affinity (K T = 290 μ M ) Na + ‐dependent process, whereas L‐[ 14 C]glutamate is taken up predominantly by a high‐affinity ( K T =6.1 μ M ) process. A bilateral kainic acid lesion reduced the V max of high‐affinity proline uptake by an average of 72%, the V max of low‐affinity proline uptake by 44%, and the V max of high affinity glutamate Uptake by 43%, without significantly changing the affinity of the transport carriers for substrate. Ipsilateral‐commissural projections of CA3 hippocampal pyramidal cells Appear to possess nearly as great a capacity for taking up proline as for taking up glutamate, a probable transmitter of these pathways. Therefore proline may play an important role in transmission at synapses made by the CA3‐derived Schaffer collateral, commissural, and ipsilateral associational fibers.