A naturally occurring compound, 6‐methoxybenzoxazolinone (6‐MBOA), present in grasses, has been shown to induce sexual maturation in a number of rodent species. The structural similarity of 6‐MBOA and melatonin has led researchers to suspect that 6‐MBOA might induce its progonadal effects by directly altering pineal function. Previous studies have shown that 6‐MBOA has the properties of a weak β‐adrenergic agonist capable of stimulating rat pineal N‐acetyltransferase (NAT) activity at pharmacological concentrations of 10−3 M. In the present study we have examined the effect of 6‐MBOA on both the pineal melatonin synthesizing enzymes, namely. NAT and hydroxyindole‐O‐methyltransferase (HIOMT) as well as on melatonin production, in organ cultured rat pineal glands. In addition, we have also examined the ability of 6‐MBOA to displace a ligand from rat brain α‐and β‐adrenoceptors. Our results confirm that 6‐MBOA stimulates NAT activity and melatonin production at the high concentration of 10−3 M. It appears to have no effect on HIOMT activity. A competition study shows that 6‐MBOA is able of displacing ligands at the α‐and β‐adrenoceptors but only at concentrations greater that 10−4 M. Whether such high concentrations of 6‐MBOA reach the pineal of rodent in their natural habitat is unknown. However, if 6‐MBOA does mediate progonadal effects by altering pineal function it would be expected that 6‐MBOA would ultimately inhibit the effects of melatonin. The possibilities are that the high melatonin levels induced by 6‐MBOA cause desensitization of melatonin receptors or that 6‐MBOA is an antagonist at the level of the melatonin receptor, thus restricting the inhibitory effects of melatonin on the reproductive system.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of pineal research|
|State||Published - Jan 1990|
- organ culture
- pineal gland
ASJC Scopus subject areas