[Study of thermoregulatory activity of a fragment of natural dermorphin precursor Arg-dermorphin and its analogs].

We studied the effect of a fragment of natural dermorphin (DM) precursor Arg-DM and its analogs (Pro-DM, 4Amino-Pro-DM, Mike et-DM, Kre-DM, Arg-[DArg2]-DM, and Arg-[DAla4]-DM after intraperitoneal administration on the functional status of the thermoregulation system in rats. The obtained data demonstrated that the hypothermic and vasomotor effects of Arg-DM were temperature-dependent and had the same pattern as DM (Emel'yanova et al., 1996). In the thermoneutral and room environment, the peptide induced a two-phase vascular response. The first phase was vasodilation; it was twice as strong as for DM and was not removed by naloxone pretreatment. The second phase was vasoconstriction; it was blocked by naloxone. Replacement of Arg with 4Amino-Pro, Met, and Kre as well as DAla2 to DArg2 or Gly4 to DAla4 replacements in the Arg-DM molecule affected the thermoregulatory activity of the peptide. For instance, only the vasodilation response was observed for Arg-[DAla2]-DM and Arg-[DAla4]-DM while only the vasoconstriction response was observed for 4Amino-Pro-DM.