ANALYSIS OF THE PEPTIDE CONTEST OF THE LOCUST VASOPRESSIN-LIKE IMMUNOREACTIVE (VPLI) NEURONS

Isolated cell bodies of the locust vasopressin-like immunoreactive (VP LI) neurons, analyzed by HPLC separation and radioimmune assay, contai n three arginine vasopressin-like peptides: a previously identified mo nomer(F1, Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2) and its antiparalle l homodimer (F2), but also the previously unreported parallel homodime r (PDm). VPLI neuron activity significantly reduces the level of cAMP in the CNS. Of the three synthetic peptides, only the monomer (F1, 10( -8) and 10(-6) M) is capable of inhibiting a forskolin-stimulated incr ease in cAMP in isolated neural membranes. The antiparallel (F2) and p arallel dimers (PDm) of this peptide have no effect on this second mes senger.