Infusion of CTAP to the nucleus accumbens core dose-dependently reduces
evoked dopamine release. The selective MOR antagonist CTAP (2, 4, and 8
μg) or saline was infused to the area of dopamine measurement via an
infusion cannula approximately 150 μm from the voltammetric electrode.
(A) Current-versus-time traces at the oxidation potential of dopamine (white, 7
seconds) are overlaid on color plots of evoked dopamine release from individual
rats before and after saline, 4 μg and 8 μg CTAP infusion. The
time of electrical stimulation is indicated by blue arrows. Infusion of 4
μg CTAP partially blunted electrically-evoked dopamine release while 8
μg CTAP blocked it. (B) and (C): Composite data show the dose-dependent
effects of CTAP on evoked dopamine release over time (B) and averaged across
post-infusion time points (C). Electrically-evoked dopamine was unchanged by
saline and 2 μg CTAP, but reduced by 4 and 8 μg CTAP. Statistics
were calculated on the data in panel C: * different from Saline, p<0.05;
# different from 2 μg CTAP, p<0.05.