Effects of natural tachykinins on ovine lower urinary tract smooth muscle.

1. Numerous studies have demonstrated that the urinary bladder is particularly sensitive to tachykinins; rat, rabbit and guinea pig bladders, besides human detrusor, have been the most extensively studied, whereas very little is known about most large animal detrusors. The aim of this work was to study natural tachykinin activity on the lower urinary tract of ovine to make a comparison with data obtained in laboratory animals. 2. As in other animal species, tachykinins are also able to contract ovine bladder smooth muscle. 3. The results reported in this study indicate that in ovine bladder, neurokinin 2 (NK2) receptors are expressed most. In fact, on lamb and sheep bladder neurokinin A (NKA), a NK2- almost selective peptide, was shown to be > 100% more active than the natural tachykinins kassinin (KASS) and eledoisin (ELED). Eledoisin was shown to be 50% less active than KASS, which is typical behaviour for an almost exclusively NK2 receptor population. Moreover, NK1- preferential peptides, namely substance P (SP) and physalaemin (PHYS), showed a lack of activity even when applied at high concentrations. 4. The results reported in this study show that lamb and sheep detrusor represent a good alternative model for the characterization of NK2-selective tachykinins.