A. Seltzer et al., MELATONIN-BINDING SITES IN BRAIN AND CAUDAL ARTERIES OF THE FEMALE RAT DURING THE ESTROUS-CYCLE AND AFTER ESTROGEN ADMINISTRATION, Endocrinology, 130(4), 1992, pp. 1896-1902
Melatonin-binding sites were studied by quantitative autoradiography i
n brain and caudal (tail) arteries and in selected brain areas of cycl
ing female rats, ovariectomized rats, and ovariectomized rats treated
with estradiol. In the caudal artery, the number of melatonin-binding
sites was significantly lower during proestrus, estrus, and metestrus
than during diestrus. In ovariectomized rats, melatonin binding to the
caudal artery was similar to that found during proestrus, estrus, and
metestrus, and a further decrease in the receptor number was produced
by estradiol replacement. Similarly, melatonin binding in anterior ce
rebral arteries was higher during diestrus than at other stages of the
estrous cycle. In ovariectomized rats, estradiol replacement also res
ulted in decreased melatonin binding in anterior cerebral arteries. Co
nversely, no changes in the number of melatonin-binding sites were obs
erved in the suprachiasmatic nucleus or the area postrema during the e
strous cycle, in ovariectomized rats, or after estradiol replacement.
The present results suggest that in the female rat, reproductive hormo
nes modulate the expression of cerebral and caudal arterial melatonin-
binding sites.