EVIDENCE FOR MULTIPLE TACHYKININ RECEPTOR SUBTYPES ON THE RABBIT IRIS SPHINCTER MUSCLE

  • 1 January 1988
    • journal article
    • research article
    • Vol. 33  (1) , 64-71
Abstract
The actions of mammalian tachykinins (substance P, substance K/neurokinin a, neuromedin K/neurokinin b) and non-mammalian tachykinins (eledosin, kassinin, physalaemin) were compared on the rabbit pupillary sphincter. All acted as direct spasmogens with potencies in the order: eledoisin > physalaemin = neurokinin b = substance P > kassinin > neurokinin a. However, their actions could be divided into at least two categories on the basis of similar kinetics of contractions, differential sensitivity to the tachykinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11) substance P and specific cross-protection against phenoxybenzamine inactivation by structurally related tachykinins. The relationship between these observations and the suggested "P" and "E" subtypes of tachykinin receptors is discussed.