Figure 2.

Urethane-anaesthetized female rat: traces showing the effects of i.v. infusion of α,β-meATP (180 nmol kg⁻¹ min⁻¹) for 5 min on bladder and urethral pressure (mmHg) and on raw external urethral sphincter (EUS-EMG) activity during the micturition reflex evoked by distension of the urinary bladder by saline (0.05 ml min⁻¹). The first panel shows the control effects of infusion of saline into the bladder (infusion on) to evoke contractions (increases in bladder pressure); after three similar contractions the infusion was stopped (infusion off) and the bladder allowed to contract isovolumetrically. At 5 min after the saline infusion had been switched off, the bladder was emptied. The second panel shows the same scenario 5 min after infusion of α,β-meATP. Note that there were no rhythmic contractions during the infusion of saline and this was associated with a maintained relaxation of the urethra and an increase in EUS-EMG activity, but these rhythmic contractions of the bladder returned on switching off the saline infusion.