Fig. 3.

(A) DA autoreceptor (DAR) sensitivity expressed as mean percentage change in accumbens DA efflux. DA efflux evoked by a test stimulus (T1) was compared to DA efflux when a second test stimulus (T2) was preceded by 1 to 40 conditioning pulses 0.3 sec prior to T2. DAT-/- mice showed much smaller reductions in DA efflux following 5, 10 and 20 conditioning pulses than the other genotypes indicating a reduced sensitivity in DARs. The vertical bars indicate the standard error of the group means. * significantly different from DAT+/+ (Dunnett's t-test). (B, left) DAT uptake efficiency at baseline (pre-nomifensine treatment) was measured as the half-life decay duration (i.e., the time for 50% decrease from the maximum evoked increase to the pre-stimulus baseline level in the amperometric signal) of the DA signal to pre-stimulation levels following 15 pulses at 50 Hz. (B, right) DAT capacity was measured by the half-life decay duration of the DA signal to pre-stimulation levels following similar stimulation in the presence of submaximal DAT blockade with nomifensine (10 mg/kg i.p.). Results indicated that DAT-/- mice differed significantly from the other genotypes in DAT efficiency and capacity, and DAT+/- mice had significantly lower DAT efficiency then DAT+/+ mice. Additionally, nomifensine significantly reduced DAT capacity in DAT+/- and DAT+/+ mice but had no-effect on DAT-/- animals. The vertical bars indicate the standard error of the group means. * groups differed significantly (simple main effects tests). # significantly different from the other genotypes (Dunnett's t-tests).