Hormonal influences on sexually differentiated behavior in nonhuman primates

Area of Science:

• Neuroendocrinology
• Behavioral Endocrinology
• Primate Models

Background:

• Sexually dimorphic behaviors in nonhuman primates are organized by prenatal androgens.
• Rhesus monkeys are a key model for studying hormonal organization of behavior.
• Historical studies used high prenatal androgen doses in female rhesus monkeys.

Purpose of the Study:

• To investigate the masculinizing and defeminizing effects of prenatal androgens on behavior.
• To examine the role of androgen metabolites and treatment timing.
• To explore the impact of anti-androgens on behavior and neuroendocrine feedback.

Main Methods:

• Prenatal exposure of female rhesus fetuses to androgens (testosterone, 5alpha-dihydrotestosterone) or anti-androgens (flutamide).
• Varied treatment durations and gestational timing (early vs. late gestation).
• Assessment of juvenile and adult copulatory behavior, sexual initiation, vocalizations, and infant interaction.

Main Results:

• High-dose androgen exposure masculinized copulatory behavior and defeminized sexual initiation.
• Non-aromatizable androgens produced similar effects, suggesting estrogenic metabolites are not critical.
• Low-dose androgens and flutamide altered infant vocalizations and interest in infants; flutamide also affected male genital development and juvenile behaviors.

Conclusions:

• Prenatal androgens have direct organizing effects on behavior and genitalia.
• The timing and dose of hormonal exposure critically influence behavioral outcomes.
• Sexually differentiated behavior results from a combination of hormonal predispositions and social experiences.