An Electrophysiological Study on the Effect of Neuropeptide Y on Sympathetic Neurotransmission in Guinea Pig Vas Deferens1

The effect of neuropeptide Y (NPY) on sympathetic neurotrans-mission to the guinea pig vas deferens was studied by recording pre- and postsynaptic electrical events with a suction electrode. When applied locally to the recording site by internal perfusion of the suction electrode, NPY inhibited both the nerve action potential (NAP) and the excitatory junction current (EJC). When applied only to the outside bathing solution, NPY had no inhibi-tory effect on the NAP or the EJC. The site of action of NPY is therefore at the presynaptic nerve terminal. The mode of action of NPY is different from those of B-HT 920, an alpha-2 adreno-ceptor agonist, and w-conotoxin, a neurotoxin that acts specifi-cally on presynaptic calcium channels. Both of these agents inhibited the EJC without any significant effect on the NAP. It is now well recognized that transmitters other than nor