Evidence for presynaptic depression of monosynaptic excitation in neonatal rat motoneurones by (1S,3S)- and (1S,3R)-ACPD.

Both the (1S,3S) and (1S,3R) stereoisomers of 1-aminocyclopentane-1,3-dicarboxylate (ACPD), but not the (1R,3R) or (1R,3S) isomers, potently depress the fastest (presumed monosynaptic) component of dorsal root-evoked ventral root potentials in hemisected isolated spinal cord of the newborn rat. This effect is not due to antagonism of known excitatory amino acid (EAA) receptors on motoneurones and may reflect an action of the two ACPD isomers at presynaptic EAA receptors of the L-2-amino-4-phosphonobutyrate (L-AP4) type.