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Abstract
Following our recent demonstration of metrazole-induced immediate-early gene expression
in the hypothalamic supraoptic nucleus (SON), we have now performed a mRNA and transcription
analysis to determine the consequences of metrazole treatment for neurohypophyseal
peptide gene expression in male rats. Levels of hypothalamic vasopressin (VP) and
oxytocin (OT) mRNA were significantly reduced at 2 and 4 h after metrazole (50 mg/kg,
i.p.), whereas pro-dynorphin mRNA was significantly elevated at 2 h. No changes in
mRNA levels were found at 8, 24 or 48 h after treatment. Another convulsant (kainic
acid, 8 mg/kg, i.p.) elicited similar effects on VP and OT mRNAs at 2 h. Specific
analysis of the SON, following metrazole, revealed an equivalent effect on VP and
OT mRNA levels but a nuclear run-on assay did not detect any change in SON VP gene
transcription at 0.5, 1 and 2 h after treatment. The results provide evidence of a
novel mechanism which may provide an additional level of control in the regulation
of neuropeptide gene expression.