Abstract
The effect of (±)-cis-2,3-piperidine dicarboxylic acid ((±)-cis-2,3-PDA) on formation of cyclic GMP by immature (7–8 day) rat cerebellar slices has been studied. Using magnesium free medium containing the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX), (±)-cis-2,3-PDA behaves as an NMDA partial agonist. Thus in this medium, (±)-cis-2,3-PDA stimulates cyclic GMP formation, an affect completely blocked by the potent, specific NMDA antagonist (±)-2-amino-7-phosphonoheptanoic acid ((±)-APH) with a K i = 17.1 μ M . The production of cyclic GMP by the full agonist (±)-trans-2,3-PDA, was also blocked by ((±)-APH, suggesting that in this preparation it activates NMDA receptors. (±)-trans-2,3-PDA was approximately half as potent as NMDA. By constructing dose response curves to NMDA in the presence of increasing concentrations of (±)-APH or (±)-APV, these compounds were shown to be competitive NMDA antagonists using Schild analysis.
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