Dynorphin A-(1-13) potently improves galanin-induced impairment of memory processes in mice.

The present study examined the effects of intracerebroventricular injection of dynorphin A-(1-13) on memory processes by using the passive avoidance task in mice. Galanin (0.3 microgram) significantly shortened the step-down latency when given 15 min before retention tests. Although dynorphin A-(1-13) (1 or 3 micrograms) did not prolong the step-down latency induced by weaker electroshocks, it inhibited the galanin (0.3 micrograms)-induced shortening of step-down latency. The effects of dynorphin A-(1-13) (3 micrograms) on the galanin-induced shortening of step-down latency were almost completely reversed by pretreatment with nor-binaltorphimine (4 micrograms), a kappa-selective opioid antagonist. These results strongly suggest that dynorphin A-(1-13) attenuates galanin-induced impairment of memory processes through the mediation of kappa-opioid receptors.