Effect of light on 5-methoxyindole-3-acetic acid in the rat.
This study aims to determine the effects of light on the levels of 5-MIAA to provide further information on this indoleamine, using a sensitive and specific radioimmunoassay (RIA) for immunoreactive 5-methoxyindole-3-acetic acid (5-MIAA) developed in our laboratories using a specific antibody and tritiated label. Significant differences were found in the immunoreactive 5-MIAA levels between mid-light and mid-dark pineal glands in rats adapted to 12/12 hrs light/dark and in constant darkness. Under constant light, the circadian rhythm was abolished. The rat serum displayed no diurnal variations in 5-MIAA levels under aux photic conditions. The persistence of rhythms found in constant darkness but abolished in constant light suggests that the pineal 5-MIAA is endogenous and uses light as an environmental cue. In addition to melatonin, 5-MIAA could possibly be another pineal photoperiodic signal in animals.
Ho
S
S
Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hung Hom.
Pang
S F
SF
Tsang
C W
CW
Tang
P L
PL
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D006897:Hydroxyindoleacetic Acid / Q000031:analogs & derivatives* / Q000097:blood*; D008297:Male; D010775:Photic Stimulation; D010870:Pineal Gland / Q000378:metabolism* / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley
C001736:5-methoxyindoleacetic acid; D006897:Hydroxyindoleacetic Acid