IDENTIFICATION AND DIURNAL STUDIES OF PINEAL AND SERUM 5-METHOXYTRYPTAMINE IN THE RAT AND QUAIL

Picomole to femtomole per gland/ml levels of 5-methoxytryptamine (5MT) in the pineal gland and serum of the rat and quail were determined, i n the absence of a monoamine oxidase inhibitor, by using the ultra-sen sitive technique of capillary column gas chromatography/electron-captu re negative ion chemical ionization mass spectrometry. Diurnal rhythms of pineal 5MT with high levels at mid-light and low levels at mid-dar k were found in both species, while serum 5MT levels showed less or no diurnal variations. The definitive presence of 5MT in the pineal glan d and blood circulation provides further evidence that it is potential ly a neurohormone. Whether 5MT is implicated in the photoperiodic resp onses and/or other physiological functions of animals, however, remain s to be investigated. (C) 1997 Elsevier Science Ireland Ltd.