Rat Fighting Behavior: Serum Dopamine-β-Hydroxylase and Hypothalamic Tyrosine Hydroxylase

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Abstract
Male Sprague-Dawley rats were subjected to 4 weeks of daily periods of immobilization stress. One of two experimental groups was allowed 1 month of recovery. After 4 weeks of stress, there was a significant increase in shockinduced fighting, in the activity of serum dopamine-β-hydroxylase, and in the activity of hypothalamic tyrosine hydroxylase. The concentration of hypothalamic norepinephrine was not decreased. After 4 weeks of recovery, only serum dopamine-βhydroxylase activity returned to normal; it therefore appears that longterm stress may increase central catecholamine synthesis. possibly resulting in a persistent increase in aggressive behavior.