Prolonged glucocorticoid exposure reduces hippocampal neuron number: implications for aging

Area of Science:

• Neuroscience
• Endocrinology
• Aging Research

Background:

• The aging hippocampus experiences neuron loss, potentially causing functional decline.
• Cumulative exposure to corticosterone (CORT) may drive this age-related neuronal loss.
• Adrenalectomy at mid-age prevents age-related hippocampal neuron loss, suggesting CORT's role.

Purpose of the Study:

• To investigate if prolonged CORT exposure accelerates hippocampal cell loss.
• To determine if CORT exposure mimics age-related changes in the hippocampus.

Main Methods:

• Rats received daily CORT injections to maintain high physiological levels.
• Animals were treated for 3 months, with some assessed 4 months post-treatment.
• Hippocampal CORT receptors, cell loss, and cell morphology were analyzed using autoradiography and cell body size distribution.

Main Results:

• Chronic CORT exposure led to persistent depletion of hippocampal CORT receptors, with no recovery after treatment cessation.
• Receptor depletion resulted from a loss of CORT-concentrating cells, particularly in the CA3 field.
• Chronic CORT treatment caused neuron loss similar in size to that seen in aged rats, and increased dark glia in CA3.

Conclusions:

• Prolonged CORT exposure accelerates age-related hippocampal neuron loss.
• Cumulative CORT exposure may contribute to age-related hippocampal neuron loss over a lifespan.
• Stress or prolonged CORT exposure can accelerate the aging process in the hippocampus.