DHEA effects on brain and behavior: insights from comparative studies of aggression

Area of Science:

• Neuroendocrinology
• Behavioral Neuroscience
• Comparative Physiology

Background:

• Traditional neuroendocrinology focused on gonadal hormones like testosterone (T) modulating brain circuits.
• Seasonal breeders exhibit aggression when gonadal T is low, suggesting alternative hormone sources.
• Adrenal dehydroepiandrosterone (DHEA) emerges as a key player in aggression during non-breeding seasons.

Purpose of the Study:

• To explore alternative neuroendocrine mechanisms regulating aggression beyond the traditional gonadal testosterone paradigm.
• To investigate the role of adrenal dehydroepiandrosterone (DHEA) in mediating aggression when gonadal steroid synthesis is suppressed.
• To understand the brain's capacity for de novo steroid synthesis and its implications for behavior.

Main Methods:

• Review of existing literature on neuroendocrinology of aggression in avian and mammalian species.
• Analysis of studies investigating adrenal DHEA and its conversion to active steroids within the brain.
• Examination of research on brain-derived steroidogenesis from cholesterol, independent of circulating levels.

Main Results:

• Adrenal DHEA is vital for aggression in species with low circulating testosterone, particularly during non-breeding seasons.
• The brain can synthesize active sex steroids from cholesterol, decoupling brain and circulating steroid levels.
• Seasonal cues like melatonin may regulate the switch between different neuroendocrine mechanisms for steroid provision.

Conclusions:

• The brain is a significant site for dehydroepiandrosterone (DHEA) synthesis and action, influencing various behaviors.
• Alternative neuroendocrine pathways involving DHEA and neurosteroids are critical for regulating aggression and other behaviors in diverse species, including humans.
• Understanding these mechanisms provides fundamental insights into the neurobiology of behavior and steroid hormone action.