The piperidine analogues prevent desensitization of glutamate receptors on crustacean muscle.

The effect of the four cis piperidine decarboxylate analogues on glutamate receptor desensitization was investigated. Intracellular recordings of the depolarization in response to ionophoretic application of L-glutamate were made from the opener muscle of the Hermit crab (Eupagurus bernhardus). Following bath application of any of the piperidine dicarboxylates (1 h) the decline in the amplitude of successive glutamate potentials in response to a train of ionophoretic pulses was prevented. This result indicated that the piperidine dicarboxylates inhibited the development of glutamate receptor desensitization. This effect was reversed on washing. During a prolonged ionophoretic glutamate application (5 s) the depolarization declined due to the onset of desensitization. This decline in the potential no longer occurred after exposure to a piperidine dicarboxylate analogue (30-60 min). Similarly, after application of the piperidine dicarboxylates the shape of the bath-applied glutamate potential was transformed from a rapid depolarization followed by repolarization to a maintained depolarization. These effects of the piperidine dicarboxylates are consistent with a loss of glutamate receptor desensitization.