Sensitivity to indomethacin of tetrodotoxin‐resistant contractions of smooth muscle from the base of rabbit bladder

Tetrodotoxin (TTX) reduced the contractions to field stimulation of strips of rabbit bladder base by 58% of control (at 40 Hz), and increased the spontaneous activity occurring between the evoked responses. The TTX-resistant contractions resembled the spontaneous activity in that they were of comparable size and poorly sustained; in the presence of indomethacin, TTX produced a significantly greater reduction (to 13% of control at 40 Hz), of the evoked contractions. Indomethacin abolished spontaneous activity in the presence and absence of TTX, but did not affect evoked responses in strips that were not exposed to TTX. The results imply that a prostaglandin-like substance may potentiate residual evoked responses in TTX-treated strips, but does not contribute to field stimulation-induced contractions in untreated bladder base smooth muscle.