A component of Premarin(®) enhances multiple cognitive functions and influences nicotinic receptor expression.
In women, ovarian hormone loss at menopause has been related to cognitive decline, and some studies suggest that estrogen-containing hormone therapy (HT) can mitigate these effects. Recently, the Women's Health Initiative study found that conjugated equine estrogens, the most commonly prescribed HT, do not benefit cognition. Isolated components of conjugated equine estrogens (tradename Premarin(®)) have been evaluated in vitro, with delta(8,9)-dehydroestrone (∆(8)E1) and equilin showing the strongest neuroprotective profiles. It has not been evaluated whether ∆(8)E1 or equilin impact cognition or the cholinergic system, which is affected by other estrogens and known to modulate cognition. Here, in middle-aged, ovariectomized rats, we evaluated the effects of ∆(8)E1 and equilin treatments on a cognitive battery and cholinergic nicotinic receptors (nAChR). Specifically, we used (125)I-labeled epibatidine binding to assay brain nicotinic receptor containing 4α and 2β subunits (α4β2-nAChR), since this nicotinic receptor subtype has been shown previously to be sensitive to other estrogens. ∆(8)E1 enhanced spatial working, recent and reference memory. ∆(8)E1 also decreased hippocampal and entorhinal cortex α4β2-nAChR expression, which was related to spatial reference memory performance. Equilin treatment did not affect spatial memory or rat α4β2-nAChR expression, and neither estrogen impacted (86)Rb(+) efflux, indicating lack of direct action on human α4β2 nAChR function. Both estrogens influenced vaginal smear profiles, uterine weights, and serum luteinizing hormone levels, analogous to classic estrogens. The findings indicate that specific isolated Premarin(®) components differ in their ability to affect cognition and nAChR expression. Taken with the works of others showing ∆(8)E1-induced benefits on several dimensions of health-related concerns associated with menopause, this body of research identifies ∆(8)E1 as a new avenue to be investigated as a potential component of HT that may benefit brain health and function during aging.
Talboom
Joshua S
JS
Department of Psychology, Arizona State University, Tempe, AZ 85287, USA. Joshua.Talboom@asu.edu
Engler-Chiurazzi
Elizabeth B
EB
Whiteaker
Paul
P
Simard
Alain R
AR
Lukas
Ronald
R
Acosta
Jazmin I
JI
Prokai
Laszlo
L
Bimonte-Nelson
Heather A
HA
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000378:metabolism; D002478:Cells, Cultured; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D004353:Drug Evaluation, Preclinical; D004966:Estrogens, Conjugated (USP) / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D006801:Humans; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects / Q000502:physiology; D010052:Ovariectomy; D051381:Rats; D011916:Rats, Inbred F344; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects
D004966:Estrogens, Conjugated (USP); D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2