DL-AP5 Sodium salt

Actions of D and L forms of 2-amino-5-phosphonovalerate and 2-amino-4-phosphonobutyrate in the cat spinal cord.[Pubmed:6145492]

Brain Res. 1982 Mar 11;235(2):378-86.

The separate optical enantiomers of 2-amino-5-phosphonovalerate (APV) and 2-amino-4-phosphonobutyrate (APB) have been tested for their ability to modify amino acid-induced and synaptic excitation of cat spinal neurones. D-(-)-APV was a highly potent and selective antagonist of amino acid-induced and synaptic excitation. Polysynaptic excitation was more susceptible to antagonism by D-APV than was monosynaptic excitation. It was considered likely that the depression of synaptic excitation by D-APV was due to the blockade of an excitatory amino acid transmitter acting at N-methyl-D-aspartate (NMDA) receptors. L-(+)-APV showed a relatively weak amino acid and synaptic blocking activity, which was similar in character to that of D-APV, and which may have been due to a slight residuum of the D isomer in the sample of the L form used. D-(-)-APB was a weak and relatively non-selective antagonist of amino acid-induced responses. In contrast, L-(+)-APB either had no effect or, at higher concentrations, enhanced these responses. Both isomers depressed synaptic responses in a proportion of the cells tested, the L form being the more potent isomer in producing this effect. Monosynaptic and polysynaptic excitations were both susceptible to this type of action. The depression of synaptic excitation by D-APB may have been due in some cases to the blockade of an excitatory amino acid transmitter. However, it is unlikely that the synaptic depressant action of L-APB is due to this mechanism.

The effects of a series of omega-phosphonic alpha-carboxylic amino acids on electrically evoked and excitant amino acid-induced responses in isolated spinal cord preparations.[Pubmed:7042024]

Br J Pharmacol. 1982 Jan;75(1):65-75.

1 The depressant actions on evoked electrical activity and the excitant amino acid antagonist properties of a range of omega-phosphonic alpha-carboxylic amino acids have been investigated in the isolated spinal cord preparations of the frog or immature rat. 2 When tested on dorsal root-evoked ventral root potentials, members of the homologous series from 2- amino-5-phosphonovaleric acid to 2-amino-8-phosphonooctanoic acid showed depressant actions which correlated with the ability of the substances to antagonize selectivity motoneuronal depolarizations induced by N-methyl-D-aspartate. 3 2-Amino-5-phosphonovalerate was the most potent substance of the series giving an apparent KD of 1.4 microM for the antagonism of responses to N-methyl-D-aspartate. 4 A comparison of the (+)- and (-)-forms of 2-amino-5-phosphonovalerate indicated that the N-methyl-D-aspartate antagonist activity and the neuronal depressant action of this substance were both due mainly to the (-)-isomer. 5 The (-)- and (+)-forms of 2-amino-4-phosphonobutyrate had different actions. The (-)-forms of this substance had a relatively weak and non-selective antagonist action on depolarizations induced by N-methyl-D-aspartate, quisqualate and kainate and a similarly weak depressant effect when tested on evoked electrical activity. The (+)-form was more potent than he (-)-form in depressing electrically evoked activity but did not antagonize responses to amino acid excitants. At concentrations higher than those required to depress electrically evoked activity, the (+)-form produced depolarization. This action was blocked by 2-amino-5-phosphonovalerate.