The role of the nucleus accumbens septi (NAS) in the behavioral action of beta-(Tyr9)melanotropin-(9-18).

In this study the effects of beta-(Tyr9)MSH-9-18 administered intracerebroventricularly (icv) or into the nucleus accumbens septi (NAS) were investigated on active and passive avoidance behavior of rats. This hypothalamic decapeptide in a dose of 1.0 microgram (icv) inhibited the extinction of active avoidance behavior however, in a dose of 0.1 microgram (icv) it was ineffective. The peptide injected into the NAS in a dose of 0.1 microgram had a same inhibitory effect but in a dose of 0.01 microgram this inhibitory effect was only a short lasting one. In the passive avoidance behavior the peptide in a dose of 1 microgram and 0.1 microgram (icv) significantly increased the passive avoidance latency, but in a dose of 0.01 microgram it was ineffective. If the same doses of the decapeptide were injected into the NAS the peptide was ineffective. These results suggest that the NAS doses not play a role in the memory effect of beta-(Tyr9)MSH9-18 and memory compound does not participate in the NAS mediated effect of the decapeptide on the active avoidance behavior.