The effects of epinephrine and norepinephrine on emotional behavior in rats and Siamese fighting fish

Abstract

In general, the purpose of the present study was to assess the effects of two catecholamines on emotional behavior. The first of three experiments was designed to investigate the effects of epinephrine and norepinephrine treatments on shock-induced reflexive fighting behavior in rats. Ss were paired and base rates of fighting behavior were established. Difference measures for each pair were obtained following injections of epinephrine, norepinephrine and saline. An analysis of these scores supported the hypothesis that injected norepinephrine would significantly increase the frequency of reflexive fighting. The hypothesis that injected epinephrine would decrease this rate was not supported. The observed effect of norepinephrine on aggressive behavior was confirmed in the second experiment using female Siamese fighting fish. Measures based on total duration of agonistic display to a mirror image supported the hypothesis that norepinephrine would potentiate the agonistic response. Latency and frequency measures, however, failed to support the hypothesis. The third experiment was designed to assess the effects of differential levels of norepinephrine on conditioned suppression of the consummatory drinking response in rats. Levels were manipulated by injection of norepinephrine, saline, and the norepinephrine inhibitor, alpha-methyldopa. The effects of this treatment were assessed under two conditions. In the first condition three groups of Ss were injected with either norepinephrine, saline, or alpha-methyldopa after mild CER training was completed. The findings revealed that norepinephrine significantly enhanced CER suppression and that norepinephrine inhibition by alpha-methyldopa attenuated suppression of the consummatory drinking response relative to the saline control. In the second condition two different groups of Ss were injected with either norepinephrine or alpha-methyldopa prior to CER training so that drug effects were contiguous with training trials. Subsequent testing 20 hours after completion of training revealed a significant enhancement of CER suppression in animals injected with norepinephrine relative to that observed in Ss treated with alpha-methyldopa. The results of these experiments were interpreted as indicating that central norepinephrine is involved as a mediator in aggression as well as "fear" and perhaps in emotional behavior generally.