Mechanisms for quick and variable responses

Dominant and subordinate males produce neuroendocrine stress responses duri ng aggressive social interaction. In addition, stress responsiveness has bo th acute and chronic temporal components. A neurochemical marker that disti nguishes social status and aggression by temporal and regional differentiat ion is the activity of serotonergic nuclei and terminals. A unique model fo r distinguishing the relationships among the neuroendocrine machinery of st ress, social status and behavior is the lizard Anolis carolinensis. Dominan t males exhibit more aggression and have temporally advanced serotonergic r esponses. Chronic serotonergic activity is associated with subordinate soci al status and reduced aggression. Acute and chronic serotonergic responses occur in both dominant and subordinate males, and are distinguished tempora lly. This provides a fundamental question that may elucidate basic differen ces in behavior: What causes temporally advanced serotonergic activity in r esponse to stress in dominant males? Secondarily, what is the neural basis for the acute and chronic responses? The neural mechanisms for transduction of the relevant behavioral signals are very plastic. Behavioral experience and visual stimuli can produce very rapid responses. Faster and greater re sponsiveness may be stimulated by restraint stress, social stress and, the absence of social sign stimuli (e.g. eyespots of the lizard Anolis caroline nsis). Stress response machinery provides regulatory factors necessary to m odify social behavior, and to adapt it for specific contexts. Serotonergic activity is rapidly modified by glucocorticoids and GABA, and also by CRF u nder conditions of previous stress or in combination with AVP. Advancing ac ute elevation of serotonergic activity may be a distinguishing characterist ic of dominant males. Social events add contextual conditioning to brain tr ansmitter activity, with social information processed in a distributed fash ion. Medial amygdala manifests delayed serotonergic response compared to hi ppocampus and nucleus accumbens, and is therefore a good candidate to media te chronic stress responsiveness. Limiting or delaying acute effects, in ad dition to chronic serotonergic activity, may be the distinguishing characte ristics of subordinate males. Monoamines, glucocorticoids, testosterone, CR F, AVP, AVT, play neuromodulatory roles producing context appropriate behav ior. Copyright (C) 2001 S. Karger AG, Basel.