Cerebrovascular melatonin MT1-receptor alterations in patients with Alzheimer's disease

The pineal hormone melatonin has two major functions: as a transducer of th e circadian day-night signal across the seasons, and as a vasoactive substa nce regulating cerebral circulation. The vasoconstrictive effects of melato nin have been postulated to be mediated by the melatonin 1a-receptor (MT1). The objective of this study was to provide the first immunohistochemical e vidence for the localization of vascular MT1 in human control hippocampus c ompared to Alzheimer's disease (AD) patients, since regional blood flow imp airments contribute to the neurodegenerative course of the disease. Both su perficial and intrahippocampal arteries revealed MT1 immunoreactivity in ad ventitia in controls, which was distinctly increased in AD patients. The in creased MT1 in AD may indicate a regulatory response to impaired melatonin levels in those patients, contributing to the regulation of cerebral circul ation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.