In 1849, Berthold demonstrated that testicular secretions are necessary for aggressive behavior in roosters. Since then, research on the neuroendocrinology of aggression has been dominated by the paradigm that the brain receives gonadal hormones, primarily testosterone, which modulate relevant neural circuits. While this paradigm has been extremely useful, recent studies reveal important alternatives. For example, most vertebrate species are seasonal breeders, and many species show aggression outside of the breeding season, when gonads are regressed and circulating testosterone levels are typically low. Studies in birds and mammals suggest that an adrenal androgen precursor-dehydroepiandrosterone (DHEA)-may be important for the expression of aggression when gonadal testosterone synthesis is low. Circulating DHEA can be metabolized into active sex steroids within the brain. Another possibility is that the brain can autonomously synthesize sex steroids de novo from cholesterol, thereby uncoupling brain steroid levels from circulating steroid levels. These alternative neuroendocrine mechanisms to provide sex steroids to specific neural circuits may have evolved to avoid the "costs" of high circulating testosterone during particular seasons. Physiological indicators of season (e.g., melatonin) may allow animals to switch from one neuroendocrine mechanism to another across the year. Such mechanisms may be important for the control of aggression in many vertebrate species, including humans.

中文翻译：

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攻击性神经内分泌调节的新机制

1849 年，Berthold 证明睾丸分泌物是公鸡攻击行为所必需的。从那时起，对攻击性神经内分泌学的研究一直由大脑接收性腺激素（主要是睾酮）的范式主导，睾酮调节相关的神经回路。虽然这种范式非常有用，但最近的研究揭示了重要的替代方案。例如，大多数脊椎动物物种是季节性繁殖者，许多物种在繁殖季节之外表现出攻击性，此时性腺退化且循环睾酮水平通常较低。对鸟类和哺乳动物的研究表明，当性腺睾酮合成低时，肾上腺雄激素前体——脱氢表雄酮 (DHEA)——可能对攻击性的表达很重要。循环中的 DHEA 可以在大脑内代谢成活性性类固醇。另一种可能性是大脑可以从胆固醇中自主合成性类固醇，从而将脑类固醇水平与循环类固醇水平分离。这些为特定神经回路提供性类固醇的替代神经内分泌机制可能已经进化，以避免在特定季节产生高循环睾酮的“成本”。季节的生理指标（例如褪黑激素）可以让动物在一年中从一种神经内分泌机制转换到另一种神经内分泌机制。这种机制对于控制包括人类在内的许多脊椎动物物种的攻击行为可能很重要。从而使大脑类固醇水平与循环类固醇水平脱钩。这些为特定神经回路提供性类固醇的替代神经内分泌机制可能已经进化，以避免在特定季节产生高循环睾酮的“成本”。季节的生理指标（例如褪黑激素）可以让动物在一年中从一种神经内分泌机制转换到另一种神经内分泌机制。这种机制对于控制包括人类在内的许多脊椎动物物种的攻击行为可能很重要。从而使大脑类固醇水平与循环类固醇水平脱钩。这些为特定神经回路提供性类固醇的替代神经内分泌机制可能已经进化，以避免在特定季节产生高循环睾酮的“成本”。季节的生理指标（例如褪黑激素）可以让动物在一年中从一种神经内分泌机制转换到另一种神经内分泌机制。这种机制对于控制包括人类在内的许多脊椎动物物种的攻击行为可能很重要。褪黑激素）可能允许动物在一年中从一种神经内分泌机制切换到另一种神经内分泌机制。这种机制对于控制包括人类在内的许多脊椎动物物种的攻击行为可能很重要。褪黑激素）可能允许动物在一年中从一种神经内分泌机制切换到另一种神经内分泌机制。这种机制对于控制包括人类在内的许多脊椎动物物种的攻击行为可能很重要。