PRESERVATION OF [I-125] GALANIN BINDING-SITES DESPITE LOSS OF CHOLINERGIC NEURONS TO THE HIPPOCAMPUS IN ALZHEIMERS-DISEASE

[I-125]Galanin binding sites were examined in the hippocampal region of patients with Alzheimer's disease (AD) and age-matched control subjects using quantitative autoradiography. In control subjects, [I-125]galanin binding sites were highly concentrated in the presubicular parvopyramidal layer (5.60 +/- 0.74 pmol/g), while other hippocampal regions had considerably lower levels of binding (0.56-1.73 pmol/g). In the majority of hippocampal regions, [I-125]galanin binding was similar in AD patients to that in controls with a significant reduction being observed only in the deep layers of the parahippocampal gyrus. The activity of choline acetyltransferase, determined in the same tissue samples used for autoradiographic studies, was markedly reduced in AD (controls 6.8 +/- 0.6; AD 2.7 +/- 0.6 nmol/h/mg protein, mean +/- S.E.M.). These data are not consistent with a presynaptic location on cholinergic terminals of galanin binding sites in the human hippocampus unless upregulation has occured.