Modulation of afferent nerve activity by prostaglandin E2 upon urinary bladder distension in rats

In overactive bladder syndrome, afferent C fibres innervating the bladder show an increased activity level. However, it remains unclear whether all C fibres are highly activated and whether A delta fibres, the other type of bladder afferent fibre, are also involved in pathological conditions. To address these questions, we analysed the relationship between bladder pressure and single-unit firing patterns of afferent nerves in the left L6 dorsal roots in living rats. The recorded fibres were classified as A delta fibres or C fibres based on the response to 0.3 mu m tetrodotoxin. Certain populations of both A delta fibres and C fibres were activated at bladder pressures below 15 cm H2O (classified as low-threshold fibres), indicating their potential contribution to detection of normal bladder filling. Intravesical administration of prostaglandin E-2 (PGE(2)) induced hyperexcitation in approximately half of such C fibres, whereas the activity patterns of low-threshold A delta fibres were unchanged. All fibres, regardless of type, which were almost silent in control conditions (classified as high-threshold fibres), were activated by application of PGE(2). Notably, the firing patterns of A delta fibres, rather than C fibres, were highly time locked to PGE(2)-induced micro-oscillation of bladder pressure. Thesemodulatory effects of PGE(2) on A delta fibres and C fibres might trigger pathophysiological activity together in overactive bladder syndrome.