Inhibition of excitatory junction potentials in guinea-pig vas deferens by alpha, beta-methylene-ATP: further evidence for ATP and noradrenaline as cotransmitters.
Excitatory junction potentials (e.j.p.s) and spontaneous excitatory junction potentials (s.e.j.p.s) recorded from guinea-pig vas deferens were greatly reduced or abolished by alpha, beta-methylene-ATP, the stable analogue of adenosine 5'-triphosphate (ATP). Brief (20-50 ms) local application of ATP by pressure ejection from a micropipette produced a transient depolarisation comparable to the e.j.p. Noradrenaline (NA) applied in a similar manner produced no such response. The depolarisation produced by the local application of ATP was also inhibited by alpha, beta-methylene-ATP. Superfusion of the tissue with ATP or NA produced depolarisation of muscle cells; in the presence of alpha, beta-methylene-ATP the depolarisation produced by ATP was almost abolished, whereas that produced by NA was not reduced. These results are consistent with the hypothesis that the e.j.p.s in the guinea-pig vas deferens are mediated by ATP, acting as a cotransmitter with NA in the sympathetic nerves supplying this organ.
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology*; D009435:Synaptic Transmission; D014649:Vas Deferens / Q000294:innervation / Q000502:physiology*
D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D009638:Norepinephrine