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Neuropeptide Y ( NPY ) functions as a neurotransmitter in
nervous system of mammalian animals. It has been shown that the
content of NPY in brain was related with the feeding behavior
and psychotic disorders, and also involved in several hormone
biosynthetic pathways such as growth hormone and thyroid
hormone. Several studies indicated that there was a closed
relationship between noradrenaline ( NA ) and NPY in both
central and peripheral neural tissues. In this study, using
northern blotting analysis, radioimmunoassay ( RIA ) and high
performance liquid chromatography-electrochemical detector (
HPLC-ECD ), the role of noradrenoceptors in the biosynthesis of
NPY was aimed to elucidation. Intracerebroventricular ( i.c.v.
) injection of a1-agonist, phenylephrine , into rat caused a
decrease in NPY content in rat cerebrocortex. This effect seems
not due to feedback regulation from the sympathetic nervous
system, and it was reversed with the selective a1A-antagonist,
WB 4101. These results suggested that the inhibition was
induced by an activation of a1-receptor. In addition , similar
treatment with the b-agonist, isoproterenol ,did not modify the
biosynthesis of NPY . However, an increase in this biosynthesis
was observed in rats that received an i.p. injection of
isoproterenol ( 4 mg / kg ). Furthermore, BRL 37344, the b3-
agonist, caused an increase in mRNA expression of NPY following
i.c.v. injection. The obtained results suggest that a1-receptor
may play an inhibitory role in the biosynthesis of NPY.
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