Prostaglandins block a Ca2+-dependent slow spike afterhyperpolarization independent of effects on Ca2+ influx in visceral afferent neurons.

The blockade of a slow Ca2+-activated K+-dependent afterhyperpolarization (AHPs) in rabbit visceral sensory neurons by the prostaglandins, PGE1 and PGD2, was investigated to determine whether the blockade was indirectly due to a reduction in Ca2+ influx. The prostaglandins (PGs) could block the AHPs in the absence of any change in Ca2+-dependent spikes elicited in the presence of tetrodotoxin and tetraethylammonium bromide. A PG-induced decrease in Ca2+-dependent spike width observed in some neurons was temporally dissociated from the PG-induced block of the AHPs. In addition, a slow afterhyperpolarization produced by the application of the Ca2+ ionophore, A23187, was blocked by the PGs. It is concluded that a reduction in Ca2+ influx is not responsible for the PG-induced blockade of the AHPs.