Abstract: Rats were trained in a shuttle avoidance task. Brain LEK levels weremeasured in rats after 5 training sessions. LEK level of stritum increasedin the rats with low performance score compared with rats with highperformance score (P<0.05) and controls (P<0.01). No difference in LEKlevel between rats with high performance score and controls was found.The data indicated that the foo?-shock stimulation was not attributableto the difference in LEK level. These results suggest that endogenousLEK may be involved in the modulation of acquisition of shuttle avoid-ance responses.

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