[Effects of gamma-oryzanol on the hypothalamo-pituitary axis in the rat]

The effects of gamma oryzanol (gamma-OZ), a ferulic acid of triterpene alcohol, on the synthesis and release of the growth hormone (GH) and prolactin (PRL) in vitro and turnover rates of hypothalamic catecholamines were investigated. A single subcutaneous injection of 20 mg/kg of gamma-OZ suppressed GH synthesis and PRL release 1 hour after the injection. gamma-OZ increased medial basal hypothalamic (MBH) dopamine (DA) content, and the DA content was decreased by a treatment of alpha-methyl-p-tyrosine (alpha MpT), a tyrosine hydroxylase inhibitor, indicating increased synthesis and release of DA in MBH by gamma-OZ. gamma-OZ did not alter norepinephrine (NE) content in MBH, while the NE content was significantly decreased, indicating unchanged synthesis and increased release of NE in MBH by gamma-OZ. These results may explain the previous data concerning the changes in serum levels of GH and PRL by gamma-OZ and also suggest that gamma-OZ can affect the synthesis and/or release of at least two hypothalamic neurotransmitters, DA and NE, resulting in the alterations of anterior pituitary hormone synthesis and/or release.