Fenfluramine challenge, self-injurious behavior, and aggression in rhesus monkeys

Area of Science:

• Neuroscience
• Primatology
• Behavioral Science

Background:

• Self-injurious behavior (SIB) and aggression in humans and primates are often associated with decreased serotonergic (5-HT) system activity.
• Understanding the neurobiological underpinnings of SIB and aggression is crucial for developing effective interventions.

Purpose of the Study:

• To investigate the relationship between serotonergic (5-HT) functioning, self-injurious behavior (SIB), and aggression in rhesus monkeys.
• To examine serum prolactin and cortisol responses to D,L-fenfluramine (FEN) as indicators of 5-HT system function in monkeys with and without a history of self-wounding (SW).

Main Methods:

• Twenty-four rhesus monkeys were administered two doses of D,L-fenfluramine (FEN) and saline controls.
• Serum prolactin and cortisol levels were measured following FEN challenges.
• Behavioral observations over 12 months assessed self-directed biting and aggression rates, correlated with hormonal responses and wounding history.

Main Results:

• Prolactin and cortisol responses to FEN did not correlate with wounding history or self-directed biting.
• A significant inverse correlation was found between aggression levels and prolactin response to FEN.
• A dose-dependent prolactin response to FEN was observed, unlike cortisol response.

Conclusions:

• The study found no evidence supporting reduced 5-HT system function in rhesus monkeys exhibiting SIB under the tested conditions.
• Results suggest an inverse relationship between serotonergic activity and aggression, with prolactin response to FEN being a potentially more sensitive indicator than cortisol.
• Further research is warranted to elucidate the complex interplay between serotonin, aggression, and SIB in nonhuman primates.