EFFECTS OF SOCIAL DOMINANCE ON THE MORPHOLOGICAL AND FUNCTIONAL ACTIVITY OF THE DIENCEPHALIC POSTERIOR TUBERCULAR DOPAMINERGIC NUCLEUS IN ZEBRAFISH (DANIO RERIO)

Abstract

Social aggression is common amongst social species. It is used to establish dominance hierarchies and allocate resources crucial for survival. While aggression can stabilize social structure, it often leads to social stress among group members, and the resulting neurobiological consequences on brain structure and function remain poorly understood. The primary objective of this thesis was to examine how established social dominance affects the structural and functional organization of the diencephalic Posterior Tubercular Dopaminergic Nucleus (PTN) in zebrafish (Danio rerio). The PTN integrates visual and olfactory information, which are relayed to the spinal cord to modulate swimming and startle escape behaviors in a status-dependent manner. Moreover, the PTN is prone to social status-dependent structural plasticity, but the physiological mechanisms remain unknown. Here, I examined the cellular mechanisms underlying the status-dependent plasticity in PTN structural and functional organization. My results show that social dominance reconfigures both the structure and activity of the PTN. Key results include: Neurogenesis contributed to the increase in PTN neuron number in dominants. Subordinate and isolated fish exhibited signs of oxidative stress. We observed status-dependent shifts in neurotransmitter identity. Dominants displayed elevated PTN activity compared to subordinates. These findings demonstrate that a combination of enhanced neurogenesis, neurotransmitter switching, and status-dependent oxidative stress shapes PTN plasticity. By showing that social dominance reconfigures the structural organization and activity of the PTN, this work provides a crucial cellular foundation and mechanism by which social experience can shape sensorimotor behavior.