Subclasses of purinoceptors in feline bladder

Purines have been shown to inhibit and excite feline detrusor smooth muscle through P1 and P2 receptor activation. Several recent studies have demonstrated differences in agonist potency orders for subclasses of purinoceptors, including P2Y and nucleotide, or P2U receptors. The current studies were performed to determine the presence of such receptor subtypes in feline detrusor smooth muscle. Cats were surgically prepared for monitoring detrusor smooth muscle contractions as increases in intravesical pressure. Contractions were induced by pelvic nerves stimulation (PNS), ATP, and ATP analogs, such as beta, gamma-methylene ATP (APPCP), 5' adenylimido diphosphate (AMP-PNP) and 2-methylthio ATP (2-MeSATP), ATP gamma S, UTP, CTP and GTP. These agents all produced contractions and had an agonist potency order of AMP-PNP = APPCP > ATP gamma S = 2-MeSATP >> ATP > UTP = CTP = GTP. The agonist potency order for inhibition of PNS nerve-evoked bladder contractions was APPCP = AMP-PNP = ATP gamma S > 2-MeSATP = ATP > UTP = CTP = GTP. Reactive Blue 2 and Coomassie's Brilliant Blue G, two putative P2Y receptor antagonists, antagonized purine-induced actions. This antagonism and the agonist potency orders suggest the possible presence of novel receptors in detrusor smooth muscle and/or the presence of multiple receptors in detrusor smooth muscle.