Rhythmic Melatonin Response of the Syrian Hamster Pineal Gland to Norepinephrine In Vitro and In Vivo
ARMY INST OF SURGICAL RESEARCH FORT SAMHOUSTON TX
Pagination or Media Count:
Norepimephrine NE, .000001 M stimulated melatonin accumulation in the incubation medium of rat but not Syrian hamster pineals taken at the end of the light phase. However, NE elevated melatonin accumulation in the medium of pineals taken after 20 min of light exposure of animals of either species at 6 h into the 10-h dark phase. A dose response to 10 to the -7 power - .00001 M NE was observed in both the medium and pineals upon incubation of pineals taken from rats at 4 h into the light phase and from hamsters after 20 min light exposure at 6 h into the dark phase. Approximately 95 of the melatonin present was in the medium. The incubation time was 4 h in all cases. Subcutaneous injection of 1 microgramg NE either at the end of the light phase or after 30 min of light at 6 h into the dark phase did not stimulate in vivo Syrian hamster pineal melatonin content determined 1 or 2 h after injection, whether the hamsters were placed in light or darkness after the injection. However, after 30 min of light beginning at 6 h into dark, injection of 5 microgramsg desipramine DMI, a blocker of catecholamine uptake into nerve endings allowed a dramatic hamster pineal melatonin response to additional injection of 1 microgramg NE, observed at 1 and 2 h in light after injection. A small effect of DMI alone was seen. DMI also potentiated the effect of NE each .000001 M on melatonin accumulation in the medium of incubated hamster pineals taken after a short light exposure at night.
- Anatomy and Physiology