Aging is associated with changes in allopregnanolone concentrations in brain, endocrine glands and serum in male rats

OBJECTIVE: Allopregnanolone is a potent neuroactive steroid hormone produced in the brain and in peripheral endocrine glands. The present study investigated possible age-related variations in allopregnanolone content in brain areas, endocrine glands and serum of male rats. DESIGN: Wistar male rats were categorized into 5 groups (6 rats in each) according to age: 6, 12, 16, 18 and 20 months respectively. METHODS: Allopregnanolone content in acidic homogenates of brain cortex, hypothalamus, pituitary, adrenals and gonads was measured by a specific radioimmunoassay. Serum allopregnanolone, corticosterone and testosterone were also assayed by radioimmunoassay. RESULTS: Brain cortex allopregnanolone content decreased significantly with age, while hypothalamic allopregnanolone content remained constant until 18 months and increased significantly at 20 months. Pituitary content showed a significant age-related reduction. Adrenal allopregnanolone content remained constant until 18 months, and was significantly higher at 20 months. Testis and serum allopregnanolone contents showed significant age-related increases. Serum testosterone levels showed an age-related decrease, while no age-related variation in serum corticosterone was found. CONCLUSIONS: The present study showed a significant impact of aging on allopregnanolone contents in brain, endocrine glands and serum, showing an age-related decrease in brain cortex and pituitary, and an age-related increase in testes, adrenals and serum.