Estrogen receptors and metabolic activity in the human tuberomamillary nucleus: changes in relation to sex, aging and Alzheimer’s disease

Abstract

The human tuberomamillary nucleus (TMN), that is the sole source of histamine in the brain, is involved in arousal, learning and memory and is impaired in Alzheimer’s disease (AD) as shown by the presence of cytoskeletal alterations, a reduction in the number of large neurons, a diminished neuronal metabolic activity and decreased histamine levels in the hypothalamus and cortex. Experimental data and the presence of sex hormone receptors suggest an important role of sex steroids in the regulation of the function of TMN neurons. Therefore, we investigated sex-, age- and Alzheimer-related changes in estrogen receptor α and β (ERα and ERβ) in the TMN. In addition, metabolic activity changes of TMN neurons were determined by measuring Golgi apparatus (GA) and cell size. In the present study, ERα immunocytochemical expression in AD patients did not differ from that in elderly controls. However, a larger amount of cytoplasmic ERβ was found in the TMN cells of AD patients. Earlier studies, using the GA size as a parameter, have shown a clearly decreased metabolic activity in the TMN neurons in AD. In the present study, the size of the GA did not change during aging, indicating the absence of strong metabolic changes. Cell size of the TMN neurons appeared to increase during normal aging in men but not in women. Concluding, the enhanced cytoplasmic expression of ERβ in the TMN may be involved in the diminished neuronal metabolism of these neurons in AD patients.