Steroid potentiation and inhibition of N-methyl-D-aspartate receptor-mediated intracellular Ca++ responses: structure-activity studies.
Pregnenolone sulfate and 15 related steroids were investigated for their effects on N-methyl-D-aspartate (NMDA)-induced elevations in intracellular Ca++ ([Ca++]i) in cultured rat hippocampal neurons by microspectrofluorimetry with the Ca(++)-sensitive indicator fura-2. Several pregn-5-ene steroids markedly potentiated NMDA-mediated [Ca++]i responses. Pregnenolone sulfate and its 21-acetoxy derivative and pregnenolone hemisuccinate were the most active. At a concentration of 50 microM, each produced approximately 300% potentiation of 5 microM NMDA responses. In addition, several steroids were identified that inhibited NMDA-induced elevations in [Ca++]i, the most potent of which was 3 alpha-hydroxy-5 beta-pregnan-20-one sulfate (IC50, 37 microM). Concentration-response curves for NMDA in the presence of active steroids revealed noncompetitive interaction(s) of these steroids with the NMDA receptor. Although the mechanism(s) responsible for either steroid-induced augmentation or inhibition of NMDA-receptor responses is unknown, these data suggest the presence of one or more steroid recognition sites with a high degree of structural specificity associated with NMDA receptors. These results further raise the possibility that pregn-5-ene 3-sulfates and pregnane 3-sulfates could be endogenous modulators of NMDA receptor-mediated synaptic events.
Irwin
R P
RP
Section on Molecular Pharmacology, National Institute of Mental Health, Bethesda, Maryland.
Lin
S Z
SZ
Rogawski
M A
MA
Purdy
R H
RH
Paul
S M
SM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011284:Pregnenolone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000502:physiology; D013329:Structure-Activity Relationship
D016194:Receptors, N-Methyl-D-Aspartate; C018370:pregnenolone sulfate; D016202:N-Methylaspartate; D011284:Pregnenolone; D002118:Calcium