Tachykinin-Induced Phosphatidylinositol Turnover in Hamster Urinary Bladder

In recent years. substance P and related tachykinins have been shown to stimulate inositol phospholipid hydrolysis in a variety of tissues, including rat salivary gland [1], guinea pig ileum longitudinal muscle and rat hypothalamus [2]. In these tissues substance P, eledoisin and substance P methyl ester possess similar nanomolar potencies at inducing this response suggesting that inositol phospholipid breakdown is associated with SP-P receptor activation [2]. However. in slices of rat ileum longitudinal muscle. eledoisin is considerably more potent than substance P at stimulating inositol phospholipid hydrolysis suggesting that in some tissues this response may be mediated by a SP-E receptor [3]. In order to investigate further the association of SP-E receptors with inositol phospholipid breakdown, we examined tachykinin-induced inositol-l-phosphate production in slices of hamster urinary bladder, a tissue whose contractile response exhibits a typical SP-E receptor profile [4].