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Binding studies of L-Prolyl-L-leucyl-glycinamide (PLG), a novel antiparkinsonian agent, in normal human brain

1983; Academic Press; Volume: 15; Issue: 1 Linguagem: Inglês

10.1016/s0031-6989(83)80079-4

1879-2936

Simon Chiu, Yu-Wah Wong, James A.J. Ferris, Rodney L. Johnson, Ram K. Mishra,

Receptor Mechanisms and Signaling

In an attempt to elucidate the mechanism subserving the potential antiparkinsonian properties of L-Prolyl-L-leucyl-glycinamide (PLG) in humans, we used a radioligand binding assay to identify specific binding sites of PLG in normal human brain. 3 H-PLG bound to crude membrane homogenates obtained from human striatum with high affinity and in a saturable manner (B max = 10.04 ± 0.82 fmoles/mg −1 protein and K D = 3.60 ± 0.43 nM). The regional distribution profile of specific 3 H-PLG binding showed that the substantia nigra exhibited the highest level of specific 3 H-PLG binding, followed by striatum and hypothalamus. Pharmacologically active analogues of PLG competed for specific 3 H-PLG binding with relative potencies correlating with their biological activities in vivo . The results are consistent with the hypothesis that specific PLG binding sites exist in the human brain capable of modulating the sensitivity of dopamine receptors.