Volume 17, Number 12,
Issue of June 15, 1997
pp. 4552-4561
Copyright ©1997 Society for Neuroscience
Neuronal Dopamine Subpopulations Maintained in Hypothalamic Slice
Explant Cultures Exhibit Distinct Tyrosine Hydroxylase mRNA Turnover
Rates
Received Jan. 28, 1997; revised March 28, 1997; accepted March 31, 1997.
Jennifer A. Maurer and
Susan Wray
Laboratory of Neurochemistry, National Institute of Neurological
Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
20892
Changes in mRNA stability have been shown to regulate critical
intracellular processes. In this investigation, we studied tyrosine
hydroxylase (TH) mRNA turnover in functionally and anatomically distinct dopaminergic (DA) populations of the rat hypothalamus. To this
end, long-term slice explant cultures from postnatal, preoptic
area/hypothalami, containing three anatomically discrete DA
populations, were generated and maintained under defined conditions. The organotypic cultures were treated with the transcription inhibitors 5,6-dichloro-1-D-ribofuranosylbenzimidazole or actinomycin D and processed for in situ hybridization histochemistry.
Relative TH mRNA content per cell was quantitated. Single-cell analysis
showed marked differences in basal TH mRNA turnover rates between DA neuronal populations. Anterior and midhypothalamic DA neurons exhibited
half-time turnovers of 9-12 and 11-23 hr, respectively. In contrast,
in the caudal hypothalamus, DA neurons of the arcuate nucleus had a
significantly lower baseline level and more rapid turnover (6-7 hr) of
TH mRNA. This investigation shows that basal turnover of a phenotypic
mRNA, TH mRNA in DA neurons, is not an intrinsic
property of the phenotypic marker. Furthermore, we found that
destabilization of TH mRNA in the caudal hypothalamus corresponds to
the known rhythmic output displayed by arcuate DA cells and, as such,
may be critical for normal function of this population. We propose that
intrinsic differences in the post-transcriptional regulation of TH
permits neuronal subpopulations, which subserve different physiological
functions, an additional mechanism to control DA biosynthesis in
response to their unique needs.
Key words:
gene expression;
mRNA stability;
organotypic;
arcuate
nucleus;
DRB;
actinomycin D