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. 1980 Jun;77(6):3729–3732. doi: 10.1073/pnas.77.6.3729

Enkephalin and fear-motivated behavior.

H Rigter, R A Jensen, J L Martinez Jr, R B Messing, B J Vasquez, K C Liang, J L McGaugh
PMCID: PMC349692  PMID: 6997883

Abstract

Leu[Enkephalin (400.0 micrograms/kg) and the enkephalin analog [DAla,DLeu]enkephalin (0.4, 4.0, and 40.0 micrograms/kg) were intraperitoneally administered to rats 5 min before they were trained on aversively motivated tasks. The peptides impaired acquisition of a one-way active avoidance response, facilitated acquisition of an inhibitory avoidance response, and had no effect on acquisition of a swim-escape response. The data indicate that the enkephalin effects are not mediated through actions on locomotor activity, pain perception or reactivity, or light sensitivity. Rather, we suggest that [Leu]enkephalin and its analog strengthen the tendency of rats to suppress behavior in the presence of cues previously associated with aversive stimulation. This effect may be due to an enkephalin-induced increase in fear or arousal. The enkephalin effect on behavior was obtained at low doses and was observed within a few minutes after administration. These findings are consistent with the interpretation that enkephalin effects may be initiated at a peripheral site.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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