-transparent.png){kind=logo}
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.
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
February 1971,
Physiology & behavior,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
May 1996,
Pharmacology, biochemistry, and behavior,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
October 1970,
Brain research,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
December 1979,
Behavioural processes,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
October 1963,
Journal of comparative and physiological psychology,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
June 1975,
Psychological reports,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
July 1957,
The Journal of pharmacology and experimental therapeutics,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
August 1966,
Psychological reports,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
December 2015,
Physiology & behavior,
H Rigter, and
R A Jensen, and
J L Martinez, and
R B Messing, and
B J Vasquez, and
K C Liang, and
J L McGaugh
January 1967,
Acta biologiae experimentalis,
