Differences in the responses to purinergic nerve stimulation and applied ATP in the guinea-pig vas deferens.
The responses to sympathetic nerve stimulation and to applied ATP in the guinea-pig vas deferens were compared. Nifedipine (10 microM) markedly reduced the non-adrenergic neural contraction but only partially blocked the contractions produced by bath-applied ATP. Suramin (300 microM) also markedly reduced the contractile responses produced by nerve stimulation, but had no significant effect on the contractions produced by bath-applied ATP. Using intracellular recording techniques, nerve stimulation was shown to produce an excitatory junction potential which was abolished by suramin (1 microM). Ionophoretic application of ATP and bath-applied ATP also produced a depolarization. Suramin (1 microM) failed to abolish the response to bath-applied ATP and enhanced the ionophoretically induced depolarization. These results suggest either that ATP is not a transmitter in the vas deferens or that two classes of purinoceptor are present, one suramin-sensitive receptor which produces a contraction via the opening of voltage-dependent Ca2+ channels, and another which is suramin-resistant and produces a contraction by another means.
Reilly
M J
MJ
Department of Zoology, University of Melbourne, Parkville, Australia.
Hirst
G D
GD
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006168:Guinea Pigs; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D013498:Suramin / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects*
D013498:Suramin; D000255:Adenosine Triphosphate; D009543:Nifedipine