Desensitization of the guinea‐pig urinary bladder by the enantiomers of adenylyl 5′‐(β,γ‐methylene)‐diphosphonate and by substance P

Adenosine 5'-triphosphate (ATP), substance P (SP) and non-cholinergic nerve stimulation contracted the guinea-pig urinary bladder. SP and two poorly-degradable analogues of ATP, the enantiomers of adenylyl 5'-(beta, gamma-methylene)-diphosphonate (AMP-PCP and L-AMP-PCP), were used to desensitize the guinea-pig bladder. Desensitization of the bladder by AMP-PCP (50 microM) or by L-AMP-PCP (50 microM) abolished the responses to ATP, and inhibited the responses to non-cholinergic nerve stimulation and to SP. The responses to histamine were unaffected. Desensitization by SP (1 microM) inhibited the responses to SP itself, but not the responses to ATP, L-AMP-PCP or non-cholinergic nerve stimulation. These results suggest that SP may act partly by releasing ATP, and support the suggestion that ATP rather than SP is the non-cholinergic stimulatory transmitter.