[Paradoxical correlations of the effectiveness of the intranasal and intraperitoneal administration of dermorphins in rats].

The analgetic activity of dermorphin and its analogue A-2 was assessed by the tail-flick test. Following intraperitoneal administration at doses 5 mg/kg and above the peptides showed significant effects. After intranasal application of the peptides a significant effect was observed in the range of low doses 0.001-0.1 mg/kg. After intranasal application of high dermorphin doses (1 or 5 mg/kg) the analgetic activity decreased. The effect of analogue A-2 lasted longer after intranasal, than after intraperitoneal administration. It is assumed that the neurophysiological mechanisms of the analgetic activity of dermorphins depend on the route of their administration.