[Analgesic activity of nucleoamino acid analogs of neuropeptides injected intracisternally and intravenously in mice].

The antinociceptive activity of several enkephalin and kyotorphine analogues having nonproteinogenic nucleoamino acids: adenyl alanine, thyminyl alanine or uracilyl alanine in their structure was studied by the method of tail clip stimulation in mice. Kyotorphine and its analogues administered intracisternally to mice were found to inhibit the nociceptive responses only at doses similar to toxic ones. At the same time among nucleoamino acid analogues of enkephalins compounds were detected which possessed the antinociceptive activity not only at intracisternal administration but at intravenous injection as well. Some structure-activity relationships of the compounds tested are discussed.