Social interaction over time, implications for stress responsiveness.

Behavioral interaction during social situations is a continuum of action, response, and reaction. The temporal nature of social interaction creates a series of stressful situations, such as aggression, displacement from resources, and the variable psychological challenge of adapting to dynamic social hierarchies. The ebb and flow of neurochemical and endocrine secretions during social stress provide a unique tool for understanding individualized responses to stress. Each social station is an adaptive response to a stressful social condition, resulting in unique neuroendocrine and behavioral responses. By examining the temporal changes of limbic monoamines and plasma glucocorticoids, aspects of mechanisms for adaptation emerge. The similarity of temporal patterns induced by social stress among fish, reptiles and primates are remarkable. Even different specific coping mechanisms point out the similarity of vertebrate stress responses. The lizard Anolis carolinensis exhibits a unique sign stimulus generated during social stress by the sympathetic nervous system that serves as a temporal landmark to distinguish neuroendocrine patterns. During social interaction dominant males have a shorter latency to eyespot darkening than opponents, inhibiting aggressive display. Eyespot coloration can be delayed using a serotonin reuptake inhibitor, causing dominant social status in many animals to be lost. Reversal of social status via serotonergic activation appears to mimic chronic serotonergic activity. The pattern of eyespot darkening, faster in dominant males, is coincident with that for serotonergic activity. The fundamental temporal relationship between dominant and subordinate limbic monoaminergic activity over a continuous course of social interaction appears to be a two-phase response, temporally specific to brain region, and always faster in dominant individuals.