Psychoneuroendocrinology of aging: the brain as target organ of hormones

Memory after menopause: preliminary considerations of hormone influence on cognitive functioning

Oestrogen has been shown to have a wide variety of organisational and activating effects on brain structure and function. Despite the significant amount of research investigating the relation and effects of oestrogen to cognitive performance in menopausal women over the past two decades, studies have failed to produce consistent findings. This paper reports on evaluations of eighty-one community-based postmenopausal Australian women comparing current, past and never users of hormone therapy (HT) on a wide range of cognitive measures of general, verbal and visual memory, delayed recall, attention, concentration and verbal comprehension. Few significant differences were found among the three groups in the demographic profile, health status or psychological functioning. Although never users had significantly lower scores on verbal memory than past users, the differences were not statistically significant when adjustments were made controlling for age, education level, verbal comprehension, attention and concentration. These findings challenge long-held beliefs regarding the usefulness of oestrogen supplements as a protective factor against cognitive decline in older women's later years.

Short-time effects of neuroactive steroids on rat cortical Ca2+-ATPase activity

Recent experimental evidence indicates that some steroid hormones, apart from their well-documented genomic actions, could produce non-genomic rapid effects, and are potent modulators of the plasma membrane proteins, including voltage- and ligand-operated ion channels or G protein-coupled receptors. Neuroactive steroids, 17beta-estradiol, testosterone, pregnenolone sulfate and dehydroepiandrosterone sulfate, after a short-time incubation directly modulated the activity of plasma membrane Ca2+-ATPase purified from synaptosomal membranes of rat cortex. The sulfate derivatives of dehydroepiandrosterone and pregnenolone applied at concentrations of 10-11-10-6 M, showed an inverted U-shape potency in the regulation of Ca2+-ATPase activity. At physiologically relevant concentrations (10-8-10-9 M) a maximal enhancement of the basal activity reached 200%. Testosterone (10-11-10-6 M) and 17beta-estradiol (10-12-10-9 M) caused a dose-dependent increase in the hydrolytic ability of Ca2+-ATPase, and the activity with the highest concentration of steroids reached 470% and 200%, respectively. All examined steroids decreased the stimulatory effect of a naturally existing activator of the calcium pump, calmodulin. The present study strongly suggests that the plasma membrane calcium pump could be one of the possible membrane targets for a non-genomic neuroactive steroid action.

Neuroactive steroids modulate in vitro the Mg(2+)-dependent Ca(2+)-ATPase activity in cultured rat neurons

1. The in vitro effect of neuroactive steroids on the Mg(2+)-dependent Ca(2+)-ATPase activity in neuronal membranes isolated from primary cell culture of rat cortex was examined. 2. A 1-hr treatment of neuronal cell culture with 17-beta-estradiol (10 pM) and pregnenolone sulfate (1 microM) resulted in an increase in the enzyme activity of as much as 130% and 160%, respectively. 3. Neuroactive steroids moderately decreased the stimulation of the Mg(2+)-dependent Ca(2+)-ATPase activity by 72 nM calmodulin, by 20-30%. 4. The effects of hormones on the ATPase activity were irreversible after extensive washing of the membranes. 5. These results suggest that 17-beta-estradiol and pregnenolone sulfate at physiological concentrations could participate in the regulation of neuronal calcium homeostasis at a membrane level.

Aging in the hippocampus: interrelated actions of neurotrophins and glucocorticoids

Over the past two decades, evidence has been accumulating that diffusible molecules, such as growth factors and steroids hormones, play an important part in neural senescence, particularly in the hippocampus. There is also evidence that these molecules do not act as independent signals, but show interrelated regulation and cooperative control over the aging process. Here, we review some of the changes that occur in the hippocampus with age, and the influence of two classes of signaling substances: glucocorticoids and neurotrophins. We also examine the interactions between these substances and how this could influence the aging process.

Possible acceleration of age effects on cognition following menopause

Many cognitive functions have been shown to deteriorate with age. Because of the importance of the menopause as a milestone in the life cycles of women, we examined whether the aging-over-time process in some cognitive functions differs between women of reproductive age and postmenopausal women. It is demonstrated here that in some cognitive tests, including driving simulation, reaction time and some visuospatial tests, there is a significant acceleration in deterioration of functioning following menopause. It is suggested that this acceleration might be associated with the lack of gonadal hormones or other reproduction-related factors which may play a protective role against age-related deterioration in some cognitive functions in women.