[Memory-enhancing effects of argipressin and its relationship with periaqueductal gray]

Wistar rats were trained to perform shuttle-box active avoidance response. In experiment A, 43 rats were implanted cannulae in bilateral periaqueductal gray (PAG) and argipressin (Arg) was injected. Arg 0.15 or 0.3 ng but not 0.05 ng retarded the extinction of avoidance response. In experiment B, 37 rats were set up bilateral electrolytic lesions of PAG or sham lesioned. Arg (6 micrograms.kg-1, ip) was injected after training. PAG lesions blocked the influence of ip Arg on memory enhancement. The results indicated that Arg may act directly on CNS to modulated memory and PAG may play an important role in this process. This observation provided further support to the previous suggestion that certain limbic midbrain structures were involved in memory-enhancement by Arg.