Nonapeptides and the evolutionary patterning of sociality

Area of Science:

• Neuroendocrinology
• Comparative neurobiology
• Behavioral neuroscience

Background:

• Neuropeptides of the arginine vasotocin (AVT) family, including arginine vasopressin (AVP) and oxytocin (OXT), are involved in neuroendocrine regulation.
• AVT/AVP circuits exhibit both conserved and rapidly evolving functions and anatomy across species.
• Medial bed nucleus of the stria terminalis (BSTm) circuits, distinct from hypothalamic projections, mediate species-specific affiliative behaviors.

Purpose of the Study:

• To investigate the role of BSTm AVT neurons in mediating social behaviors.
• To understand the evolutionary divergence of AVT/AVP circuits in relation to sociality and mating systems.
• To compare the functional profiles of BSTm and hypothalamic AVT/AVP neurons.

Main Methods:

• Analysis of Fos expression in AVT neurons in response to social stimuli.
• Comparison of AVT neuron number and V(1a)-like receptor binding density in gregarious versus territorial songbirds.
• Infusion of AVT into the lateral septum to assess effects on aggression.

Main Results:

• BSTm AVT neurons show increased Fos expression in response to positive social stimuli, but not negative stimuli.
• Gregarious songbirds exhibit higher Fos induction, baseline Fos expression, more BSTm AVT neurons, and greater V(1a)-like binding in the lateral septum compared to territorial species.
• Septal AVT infusions inhibit resident-intruder aggression but facilitate mate competition aggression.

Conclusions:

• BSTm AVT circuits play a crucial role in affiliative behaviors and show rapid, species-specific evolution.
• Differences in BSTm and hypothalamic AVT/AVP circuitry may determine approach-avoidance behaviors and be targets of natural selection related to sociality.
• The distinct functional profiles of BSTm and hypothalamic AVT/AVP neurons highlight the complex modulation of social behavior by nonapeptide systems.