Effect of [DAla4]-Dermorphin and Its Analogs on the Functional Status of the Thermoregulation System in Rats at Different Environmental Temperature

We studied the influence of DAla⁴]-dermorphin (DAla⁴]-DM), its fragments (DAla⁴]-DM_2–7, DAla⁴]-DM_3–7, and DAla⁴]-DM_4–7) and analogs (Trp¹, DAla⁴]-DM, DArg², DAla⁴]-DM, and DOrn², DAla⁴]-DM) on the functional status of the thermoregulation system in rats at different thermal environments: cold (4–6°C), thermoneutral (27–28°C) and hot (31–32°C). DAla⁴]-DM administration proved to induce temperature- and dose-dependent hypothermia and vasomotor responses. No activity of the peptide was observed in the hot environment. N-terminal shortening of the peptide inhibits its thermoregulatory activity. Tyr¹ to Trp¹ substitution nearly completely suppressed the thermoregulatory effects. DAla² to DArg² substitution decreased the hypothermic effect and only the vasodilatory response was observed in the comfortable environment. DAla² to DOrn² substitution completely suppressed the hypothermic effect in the cold environment and considerably attenuated the vasodilatory response in the thermoneutral environment.