Journal of Neuroscience, Vol 7, 1648-1654, Copyright © 1987 by Society for Neuroscience
Increased dopamine efflux from striatal slices during development and after nigrostriatal bundle damage
MK Stachowiak, RW Keller Jr, EM Stricker and MJ Zigmond
Dopaminergic control over striatal targets appears to be retained in rats
sustaining lesions of the nigrostriatal dopamine (DA) system as long as
5-10% of that projection remains. Similarly, during postnatal development,
dopaminergic control over striatal neurons matures well before the
innervation of striatum by the nigrostriatal bundle is attained. These
observations suggest that enhanced efficacy of dopaminergic transmission
may compensate for hypoinnervation of striatum after lesions or during
development. To examine this hypothesis, striatal slices were superfused
with Krebs bicarbonate buffer and effluent was collected and analyzed for
endogenous DA. Electrical field stimulation (2 Hz) continuously delivered
to slices prepared from intact adult rats increased DA efflux to 3-5 times
the prestimulation rate within 10 min. Efflux then fell to approximately
twice the basal rate over the next 20 min. DA efflux was also examined
using slices prepared from adult animals given 6-hydroxydopamine 2-3 weeks
earlier, and from 7-10-d-old rat pups. In each group, striatal DA levels
were 10-40% of adult control values. Nevertheless, stimulated DA efflux
from these slices attained the same rate as that observed with intact,
adult slices. Thus, fractional DA efflux from these slices was several
times higher than the control rate by the end of the stimulation period.
This increased DA efflux appeared to be a consequence of both increased
release and decreased reuptake of DA, as the fractional DA efflux from
control striatal slices could not be increased to the rate seen in
hypoinnervated slices using nomifensine (10 microM), an inhibitor of DA
efflux.(ABSTRACT TRUNCATED AT 250 WORDS)