Desensitisation of substance P decreases the contractile effect of M15 and Gal (1-14)-(Abu 8) SCY-I on the rat gastric fundus.

Tachyphylaxis to SP decreased the effect of M15 and Gal(1-14)-[Abu8]SCY-I on gastric smooth muscles, without effect on the action of Gal. These findings support our initial hypothesis: the action of M15 and Gal(1-14)-[Abu8]SCY-I on the smooth muscles may not only be due to their agonist activity at Gal receptors, but may result from a subsequent stimulation of receptors for SP and perhaps for other tachykinins as well, however, a possibility that Gal analogues release endogenous SP can not be excluded. Further studies involving a tachykinin antagonist (spantide) are in progress at the moment. [1].