title: Classification and properties of acidic amino acid receptors in hippocampus. III. Supersensitivity during the postnatal period and following denervation.
abstract: The effects of excitatory amino acids on 22Na efflux rate in rat hippocampal slices were determined at various postnatal days and following removal of a major afferent system. Two weeks after a unilateral hippocampal aspiration, the 22Na efflux induced by potassium ions, D-glutamate, N-methylaspartate, and kainate is significantly decreased in the contralateral intact hippocampus whereas the effect of L-glutamate is substantially increased. Analysis of concentration-response curves suggests that the increased responsiveness to L-glutamate is due to an increase in the maximal effect rather than to changes in the half-maximal concentration for the amino acid. Partial denervation does not detectably change efflux elicited by D,L-homocysteic acid nor does it modify the properties of [3H]glutamate binding to hippocampal membranes. The effects of potassium ions, N-methylaspartate, and kainate but not of D,L-homocysteate are significantly decreased in slices incubated in the absence of calcium. All of the amino acids tested are considerably more potent in slices prepared from 11-day-old rats than in those from adult rats; the differences in responsiveness reflect an increase in maximal effect without changes in the half-maximal concentration. The responses to L-glutamate and D,L-homocysteate decline steadily between postnatal days 11 and 30, at which time adult values are reached. Together, the results from the denervation and development studies suggest a different localization and different modes of regulation for various classes of excitatory amino acid receptors.
mesh_terms: D000375:Aging; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003714:Denervation; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000254:growth & development / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000145:classification*; D012964:Sodium / Q000378:metabolism
chemical_list: D005971:Glutamates; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D018698:Glutamic Acid; D012964:Sodium