Fig. 4.

Dose-response relationship for capsaicin-evoked CGRP release before and after sustained morphine treatment. DRG neurons (7 days in culture) were incubated without (▪) or with (▴) morphine (1 μM) for 24 h followed by stimulation (10 min) with various doses of capsaicin ranging from 10 nM to 3 μM. CGRP release (mean ± S.E.M.) is expressed as the percentage of basal CGRP release (610 ± 22 pg/ml) from unstimulated DRG neurons. The dose-response curves show the mean ± S.E.M. of three individual experiments, performed in quadruplicates.