Pre- and postjunctional effects of diadenosine polyphosphates in the guinea-pig vas deferens.

Abstract The pre- and postjunctional activities of a number of diadenosine polyphosphates were examined in the guinea-pig isolated vas deferens at the level of the membrane-potential, using a modified sucrose-gap technique. P1,P3-Di(adenosine 5′)triphosphate (Ap3A), P1,P4-di(adenosine 5′)tetraphosphate (Ap4A) and P1,P5-di(adenosine 5′)pentaphosphate (Ap5 A) all caused concentration-dependent depolarization of the smooth muscle membrane. The potency order was: Ap5A > Ap4A. Ap3A. P1, P2-Di(adenosine 5′)pyrophosphate (Ap2A) did not evoke depolarization even at the highest concentration tested (1 mM). All the dinucleotides caused a reduction in the amplitude of evoked excitatory junction…