Evidence against VIP or substance P being the transmitter in non-cholinergic excitatory nerves supplying the guinea-pig bladder.

In the guinea-pig bladder, contractile responses to substance P (0.3 microM) and VIP (3 microM) were unaffected by P2-purinoceptor desensitization with alpha,beta-methylene ATP (3 X 10(-6) M), while the responses to stimulation of the non-cholinergic excitatory nerves (4-16 Hz) were abolished. The evidence presented suggests that ATP or a related purine nucleotide, and not VIP or substance P, is responsible for the non-cholinergic excitatory component of the nerve-mediated response.