ADRENALECTOMY DECREASES VASOACTIVE-INTESTINAL-PEPTIDE MESSENGER-RNA LEVELS IN THE RAT SUPRACHIASMATIC NUCLEUS

Vasoactive intestinal peptide (VIP) concentrations were shown to be re gulated by adrenal steroids. Therefore, we investigated whether adrena l steroids affect VIP mRNA levels, which would suggest an effect on VI P mRNA expression. Adrenalectomy performed on adult male rats resulted in a significant decrease in VIP mRNA in the hypothalamus (from 10.6 +/- 0.3 to 3.5 +/- 0.2 arbitrary units). In situ hybridization experim ents revealed that a major site of VIP mRNA expression in the hypothal amus is the suprachiasmatic nucleus. Indeed, adrenalectomy resulted in an approximate decrease by half in VIP transcripts in this nucleus. H owever, this decrease was not reversed by replacement treatment with c orticosterone or the glucocorticoid agonist, RU28362. Thus, VIP mRNA m ay be regulated by indirect mechanisms, influenced by the adrenal glan d.