Figure 5. Suppression of recurrent inhibition after systemic naloxone.
A–C, recurrent inhibition of bladder C fibre reflexes as observed before (A) and after naloxone (0.05 mg kg−1i.v.; B and C); left control, right conditioned response. Test stimulation intensity was the same for records in A and B (50 × threshold for the Aδ reflex) but decreased in C (20 × threshold) to match the control response in A; other stimulation parameters remained the same throughout. Note that the recurrent inhibition was abolished by naloxone, even after the decrease in test stimulation intensity. D, graphic illustration of the same effect showing conditioned reflex sizes (as a percentage of control) before (○) and after naloxone (•). The latter points were obtained during 4 conditioning trials in the 30 min period following naloxone administration. The time of conditioning stimulations of the contralateral BPN is indicated by the grey bar.