Pineal influence on intermale aggression in adult house mice.

Area of Science:

• Neuroendocrinology
• Behavioral Neuroscience
• Animal Behavior

Background:

• The pineal gland, historically linked to circadian rhythms, also influences various physiological processes.
• Interactions between the pineal gland, social behavior, and reproductive function in mammals require further elucidation.

Purpose of the Study:

• To investigate the role of the pineal gland in regulating intermale aggression and social hierarchy in adult male mice.
• To determine if pinealectomy affects the physiological responses to social subordination and influences reproductive organ function.

Main Methods:

• Adult male mice were subjected to either sham surgery or pinealectomy (pinx).
• Following a 14-day recovery period, mice were assessed for aggressive behavior during pairings and social interactions in grouped housing.
• Physiological parameters including adrenal gland weight, body weight, thymus weight, seminal vesicle weight, and wounding were measured.

Main Results:

• Pinealectomy significantly increased the latency to initiate fighting and reduced fighting duration.
• Sham males exhibited dominance over pinealectomized males in 75% of pairings.
• Pinealectomized subordinates showed increased adrenal weight, greater wounding, lighter thymus glands, and reduced body weight compared to sham subordinates, but prevented seminal vesicle atrophy.

Conclusions:

• The pineal gland plays a crucial role in modulating intermale aggression and social dominance in mice.
• Pinealectomy exacerbates the physiological stress response to social subordination but preserves seminal vesicle function.
• These findings highlight the pineal gland's function in integrating social stimuli with neuroendocrine and reproductive outcomes.