L-trans-2,3-pyrrolidine dicarboxylate: characterization of a novel excitotoxin.
This study investigated the in vitro and in vivo excitotoxic properties of a novel conformationally constrained analogue of L-glutamate, L-trans-2,3-pyrrolidine dicarboxylate (L-trans-2,3-PDC). When tested for excitotoxic activity in rat cortical cultures, L-trans-2,3-PDC mimicked the action of NMDA in both acute (30 min) and chronic (24 h) exposure paradigms. This neurotoxicity was attenuated by co-addition of MK-801 (10 microM). Microinjections of L-trans-2,3-PDC into the dorsal hippocampus of male rats also induced a selective pattern of pathology indicative of an NMDA receptor excitotoxin. In contrast to the equipotency observed in vitro, 100 nmol of L-trans-2,3-PDC were needed to produce cellular damage comparable to that induced by 25 nmol of NMDA. Consistent with an action at NMDA receptors, L-trans-2,3-PDC-induced damage could be significantly reduced by co-administration of MK-801 (3 mg/kg i.p.), but not by NBQX (25 nmol). In radioligand binding assays L-trans-2,3-PDC inhibited the binding of 3H-L-glutamate to NMDA receptors (IC50 1 microM), although it also exhibited some cross reactivity with KA and AMPA receptors. L-trans-2,3-PDC was also identified as a competitive inhibitor (Ki = 33 microM) of 3H-D-aspartate uptake into rat forebrain synaptosomes. In contrast to the action of a transported substrate, such as L-glutamate, L-trans-2,3-PDC did not exchange with 3H-D-aspartate that had been previously loaded into the synaptosomes.
Willis
C L
CL
Department of Pharmaceutical Sciences, University of Montana, Missoula 59812, USA.
Humphrey
J M
JM
Koch
H P
HP
Hart
J A
JA
Blakely
T
T
Ralston
L
L
Baker
C A
CA
Shim
S
S
Kadri
M
M
Chamberlin
A R
AR
Bridges
R J
RJ
D000818:Animals; D002452:Cell Count / Q000187:drug effects*; D002478:Cells, Cultured / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects*; D003998:Dicarboxylic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology*; D009498:Neurotoxins / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D003998:Dicarboxylic Acids; D009498:Neurotoxins; D011759:Pyrrolidines; C103758:pyrrolidine-2,3-dicarboxylic acid; D016202:N-Methylaspartate