Abstract
Brain norepinephrine metabolism and catecholamine synthesis were measured in rats subjected to electric footshock in the presence or absence of another subject. Animals shocked in pairs engaged in fighting behavior, whereas animals receiving shock without another rat present could not fight. Marked differences in the metabolism of norepinephrine formed from intracisternally injected 3H-dopamine were found in the two groups receiving footshock. Within each experimental group, alterations in norepinephrine metabolism showed anatomic specificity, and temporal effects on metabolism in various brain regions were observed at various intervals after presentation of footshock. The observed changes in norepinephrine metabolism suggest that, in rats receiving footshock without a partner, norepinephrine turnover in the medulla-pons specifically increases during the shock period; during the 1 hour period postshock, however, norepinephrine turnover in the medulla-pans is decreased. 3H-normetanephrine levels are decreased markedly at all times, suggesting that norepinephrine metabolism in the medulla-pons is primarily deaminative (via monoamine oxidase intraneuronally) in the face of the shock procedure. In contrast, rats shocked in pairs, thereby eliciting fighting responses, show no alterations in regional norepinephrine metabolism during the period of shock but have elevated norepinephrine turnover rates in both medulla-pons and diencephalon during the subsequent 1-hour period. This change is accompanied by a slight shift in metabolism toward normetanephrine. Studies of catecholamine synthesis from 3H-tyrosine revealed no significant changes in amine formation in rats shocked alone, but norepinephrine formation in fighting rats was elevated. Furthermore, within the fighting group there was a significant positive correlation between the number of fights and the degree to which norepinephrine synthesis was increased.
Footnotes
- Received June 21, 1973.
- Accepted April 22, 1974.
- © 1974 by The Williams & Wilkins Co.
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