Sex-specific endocrine regulation of seasonal aggression in Siberian hamsters

Coordinating physiological and behavioural processes across the annual cycle is essential in enabling individuals to maximize fitness. While the mechanisms underlying seasonal reproduction and its associated behaviours are well-characterized, fewer studies have examined the hormonal basis of non-reproductive social behaviours (e.g., aggression) on a seasonal timescale. Our previous work suggests that the pineal hormone melatonin facilitates a ‘seasonal switch’ in neuroendocrine regulation of aggression in male and female Siberian hamsters (Phodopus sungorus), specifically by acting on the adrenal glands to increase the production of the androgen dehydroepiandrosterone (DHEA) during the short-day (SD) photoperiods of the non-breeding season. Here, we provide evidence that the activity of 3β-hydroxysteroid dehydrogenase/∆5-∆4 isomerase (3β-HSD), a key enzyme within the steroidogenic pathway that mediates DHEA synthesis and metabolism, varies in a sex-specific and melatonin-dependent manne...