Guinea pig ileum test

The guinea-pig ileum test has been developed [242, 243] to provide quantitative data upon the agonist and antagonist properties of morphine-like drugs. The agonist activity is measured by the concentration of drug which causes 50 per cent depression of the twitch induced by coaxial stimulation (IDso value) and the antagonist activity by the equilibrium constant (A)g). The latter is obtained... 

Synthetic dermorphin tetrapeptides (small dermorphins), e.g. Tyr-D-Ala-Phe-Gly, and PMRI isomers (partially modified retro-inverso isomers) synthesized by Tomatis et al.54) are more effective than morphine or dermorphin in the GPI test (guinea-pig ileum test). 

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