N. Murakami et al., COMPARISON OF CIRCADIAN OSCILLATION OF MELATONIN RELEASE IN PINEAL CELLS OF HOUSE SPARROW, PIGEON AND JAPANESE-QUAIL, USING CELL PERFUSION SYSTEMS, Brain research, 651(1-2), 1994, pp. 209-214
We compared the circadian oscillation of melatonin release from cultur
ed pineal cells in Japanese quail, pigeon and house sparrow, to determ
ine whether the pineal gland of these species retains the circadian os
cillator function in vitro. After dissociated pineal cells have been c
ultured for 4 days under 12 h:12 h light-dark (LD) cycle, they were pe
rfused at a flow rate of 0.25 ml/h for 6-7 days under LD or constant d
arkness (DD). Melatonin release increased during the dark period and l
ow during the light period in all pineal cell cultures. Under DD condi
tions, the circadian rhythm of melatonin release persisted for up to 3
-4 cycles in pigeon and house sparrow pineal cells, but the amplitude
of the rhythm decreased gradually. However, in Japanese quail pineal c
ell culture the circadian oscillation of melatonin release was weak or
abolished under DD conditions. These results strengthen the argument
that the avian pineal gland's role in circadian organization differs b
etween species. The direct demonstration of species-specific differenc
es in the mechanism of the circadian oscillation of melatonin release
from pineal cells should provide a useful model for the analysis of th
e pineal's circadian system at the cellular level.