Journal of Neuroscience, Vol 9, 4430-4438, Copyright © 1989 by Society for Neuroscience
Effects of dopamine depletion on striatal neurotensin: biochemical and immunohistochemical studies
AJ Bean, MJ During, AY Deutch and RH Roth
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.
Interactions between striatal dopamine (DA) and neurotensin (NT) have been
suggested by anatomical, behavioral, and biochemical studies. Nigrostriatal
DA neurons, in contrast to mesocorticolimbic DA neurons, do not appear to
contain NT. Thus, distinct neuronal elements subserve interactions between
DA and NT within the striatum. We have previously demonstrated that
reserpine-induced depletion of striatal DA is accompanied by a dose- and
time-dependent increase in striatal NT concentrations. In order to further
characterize the effects of reserpine and to define the mechanism by which
reserpine acts to increase striatal NT concentrations, we have used
immunohistochemical and biochemical approaches. Immunohistochemical
examination of rats pretreated with reserpine revealed marked increases in
the density of NT-like immunoreactive (NT-li) perikarya and fibers, and the
development of NT-li patches. Pretreatment with reserpine had no apparent
effect on NT synthesis, as assessed by examination of cycloheximide-induced
inhibition of protein synthesis. However, reserpine administration resulted
in a significant decrease in the release of both DA and NT into the
striatal extracellular fluid, as measured by in vivo microdialysis. These
data suggest that the increase in striatal NT concentrations observed after
reserpine treatment results from decreased release, rather than increased
synthesis of the peptide.