Summary
Neuropeptide Y (NPY) and noradrenaline (NA) are synthesized and stored in sympathetic
nerves and concomitantly released in response to appropriate Stimuli. The two substances
have been reported to interact on various levéis: postjunctionally, by mutually potentiating
their vasoconstrictor effects, prejunctionally, by inhibiting each other's reléase.
The possibility of an interaction on the levels of their synthesis was investigated
in this study. Specific cDNA probes were used for the measurement of the steady State
levels of the mRNAs encoding prepro-NPY and tyrosine hydroxylase (TH) in the superior
sympathetic cervical and stellate ganglia of rats. Reserpine (5 mg/kg) was administered
for inducing catecholamine depletion. This caused a large decrease in the NA content
of the heart associated with an about 50% reduction in cardiac NPY levels. Ganglionic
NPY and TH mRNA levels increased 3—6 fold as compared to vehicle treated animals.
To determine whether this effect was due to transynaptic induction, superior cervical
ganglia were decentralized in a subgroup of rats. Decentralized ganglia displayed
significantly lower NPY and TH mRNA levels than intact ones. The response to reserpine
was almost completely prevented by decentralization.
These Observations indicate that the activation of gene expression of NPY and TH by
reserpine depends on intact ganglionic innervation and is therefore reflexly mediated.
Trans-synaptic induction may regúlate NPY and TH mRNA levels also under basal conditions.
Key words
sympathetic ganglia - neuropeptide Y-tyrosine hydroxylase - reserpine - gene expression
