| Popis: |
We have extended our studies on the structure-activity relationship in neuropeptide proctolin (Arg-Tyr-Leu-Pro-Thr) by evaluating the effects of a series of proctolin analogues modified in position 2 of the peptide chain, including: [Phe(p-Cl)2]- (1), [D-Phe(p-Cl)2]- (2), [N-Me-Tyr2]- (3), [D-Phe(p-NH2)2]- (4), [D-Phe(p-N,N-di-Me)2]- (5), [N-Me-Tyr(OMe)]- (6), [D-3-Pal2]- (7), [L-Nal2]- (8), [D-Nal2]- (9), [Lys(Nic)2]- (10), [D-Lys(Nic)2]- (11), [D-Phe-(p-NO2)2]- (12). These peptides were evaluated for myotropic activity on the heart of Tenebrio molitor and contractile activity of the foregut of Schistocerca gregaria. Analogues 1-5, 7-9, and 12 retained a weak cardiotropic activity in Tenebrio molitor while peptides 1, 8 and 12 preserved 15-25% of the locust-gut contracting activity of proctolin. Peptides 2, 4 and 7 showed weak inhibitory activity in Schistocerca gregaria foregut, whereas only peptides 4 and 7 reduced the maximum response to applied proctolin by 64% and 49% respectively, at the 10(-6) M concentration. |
