Design of N-acylprolyltyrosine "tripeptoid" analogues of neurotensin as potential atypical antipsychotic agents.

A series of N-acylprolyltyrosine amides was designed as tripeptoid analogues of neurotensin. The substituted dipeptides were tested in vivo for antidopamine activity by their ability to inhibit the apomorphine-induced climbing in mice and the dopamine-induced extrapolatory behavior impairment in rats. The N-acylprolyltyrosine amides structure-activity relationships have indicated the size of the N-acyl group and the configuration of amino acids that are important for the activity. We found that the bioactivity has been increased dramatically when the n-hydrocarbon chain on the N-acyl group was increased from four to five carbon atoms. The activity seems to reside exclusively in the L-Tyr diastereomers. All of the compounds tested were inactive in the cataleptogenic action and did not exhibit the acute toxicity even at doses 500-1000 times higher than ED50 in climbing test. On this basis, the N-acylprolyltyrosine amides could potentially be a novel class of atypical antipsychotic agents.