Abstract

The pharmacological properties of the κ 1 opioid receptor were investigated in human post-mortem temporal cortical membranes from control and Alzheimer's disease brains, using the κ 1-selective radioligand [ 3H]U69593. [ 3H]U69593 bound to a single high affinity site population with no significant difference between control ( B max 31 ± 4.14 fmol/mg protein, K D 1.01 ± 0.26 nM) and Alzheimer's disease brains ( B max 37 ± 4.63 fmol/mg protein, K D 0.86 ± 0.08 nM). Competition studies with dynorphin B and α-neoendorphin gave flat inhibition curves with Hill coefficients of 0.31 ± 0.04 and 0.49 ± 0.09 in the control brains and 0.38 ± 0.05 and 0.48 ± 0.08 in the Alzheimer's disease brains, respectively. The pI 50 values for dynorphin B and α-neoendorphin were 8.73 ± 0.17 and 8.48 ± 0.09, respectively, in the control brains and 9.30 ± 0.22 and 8.70 ± 0.15 in the Alzheimer's disease brains. The guanine nucleotide analogue Gpp(NH)p inhibited binding by ca. 70% in both the control and Alzheimer's disease brains, the residual binding being sensitive to NaCl in both cases. These results indicate that the pharmacological properties and the functional integrity of G-protein coupling of the κ 1 receptor recognition site are preserved in Alzheimer's disease temporal cortex.

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