[Corticoliberin fragment CRF4-6 modifies rat behavior in opposite ways under stressing and non-stressing conditions].

The effects of tripeptide corticoliberin fragment CRF4-6 (icv; 6, 30, and 150 nmol/head) on behaviour of rats were investigated under non-stressing and stressing conditions. CRF4-6 activated rat behaviour under non-stressing conditions (home cage): the duration of locomotion and exploratory behaviour was increased whereas the duration of passive behaviour and sleep was decreased. On the other hand, CRF4-6 suppressed the rat exploratory behaviour under stressing conditions (elevated plus-maze): the duration of non-exploratory behaviour was increased; numbers of rearings and leanings out to open arms were reduced. All observed effects of the tripeptide CRF4-6 were dose-dependent. Behavioural effects of the tripeptide were similar to the well-known action of the whole corticoliberin molecule. Therefore we suggest that CRF4-6 is located in the active part of CRF or it can be a physiologically active corticoliberin derivative.