Purine nucleotides inhibit the binding of DL-[3H] 2-amino-4-phosphonobutyrate (DL-[3H] APB) to L-glutamate-sensitive sites on rat brain membranes.

The effects of purine nucleotides on the binding of DL-[3H] 2-amino-4-phosphonobutyrate (DL-[3H] APB) to rat brain membranes were investigated. Certain guanine nucleotides, especially cyclic GMP and GTP, were found to be potent inhibitors of binding. Kinetic studies revealed that both cyclic GMP and GTP acted to decrease receptor affinity without affecting significantly binding site density. These endogenous substances may therefore play an important role in the regulation of excitatory amino acid receptor function.