Abstract
BackgroundAge-dependent alterations of hormonal states have been considered to be involved in age related decline of cognitive abilities. Most of the studies in animal models are based on hormonal substitution in adrenal- and/or gonadectomized rodents or infusion of steroid hormones in intact rats. Moreover, the manipulations have been done timely, closely related to test procedures, thus reflecting short-term hormonal mechanisms in the regulation of learning and memory. Here we studied whether more general states of steroid and thyroid hormone profiles, independent from acute experiences, may possibly reflect long-term learning capacity. A large cohort of aged (17–18 months) intact male rats were tested in a spatial hole-board learning task and a subset of inferior and superior learners was included into the analysis. Young male adult rats (16 weeks of age) were also tested. Four to 8 weeks after testing blood plasma samples were taken and hormone concentrations of a variety of steroid hormones were measured by gas chromatography-tandem mass spectrometry or radioimmunoassay (17β-estradiol, thyroid hormones).ResultsAged good learners were similar to young rats in the behavioral task. Aged poor learners but not good learners showed higher levels of triiodothyronine (T3) as compared to young rats. Aged good learners had higher levels of thyroid stimulating hormone (TSH) than aged poor learning and young rats. Both aged good and poor learners showed significantly reduced levels of testosterone (T), 4-androstenedione (4A), androstanediol-3α,17β (AD), dihydrotestosterone (DHT), 17-hydroxyprogesterone (17OHP), higher levels of progesterone (Prog) and similar levels of 17β-estradiol (E2) as compared to young rats. The learning, but not the memory indices of all rats were significantly and positively correlated with levels of dihydrotestosterone, androstanediol-3α,17β and thyroxine (T4), when the impacts of age and cognitive division were eliminated by partial correlation analyses.ConclusionThe correlation of hormone concentrations of individuals with individual behavior revealed a possible specific role of these androgen and thyroid hormones in a state of general preparedness to learn.
Highlights
Age-dependent alterations of hormonal states have been considered to be involved in age related decline of cognitive abilities
Thyroid hormones could be related to cognitive decline in men [11,12,13]
Four to 8 weeks after testing the blood hormone concentrations of a variety of steroid hormones were measured by gas chromatography-tandem mass spectrometry or radioimmunoassay (17β-estradiol, thyroid hormones)
Summary
Age-dependent alterations of hormonal states have been considered to be involved in age related decline of cognitive abilities. We studied whether more general states of steroid and thyroid hormone profiles, independent from acute experiences, may possibly reflect long-term learning capacity. Corticosterone application after acquisition support memory consolidation [8, 9], whereas it impairs memory retrieval when given shortly (30 min) but not hours before a memory retention test [10] Besides these steroid hormones, thyroid hormones could be related to cognitive decline in men [11,12,13]. Thyroid hormones could be related to cognitive decline in men [11,12,13] Due to this variety of neuroactive hormones that can be independently or interactively regulated, it is feasible that the individual profiles of different steroid hormones, rather than the levels of certain hormones determine the cognitive status, especially in aged subjects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
