CNS.Hypothalamo-pituitary-ovarian axis before, during and following the reproductive phase of human female' life cycle / 대한소아내분비학회지

No abstract available.

Regulation of Estrogen Receptor mRNA in Rat Anterior Pituitary Gland / 대한내분비학회지

The estrogen receptor (ER) is present in a wide variety of mammalian tissues and is required for the physiological responses of estrogen, including estrogen-induced tissue-specific changes in gene expression. But most of our knowledge on the regulation of ER mRNA levels comes from in vivo steroid replacement experiments or cancer cell lines that express the ER. Thus the present study was attempted to determine 1) the anterior pituitary ER mRNA levels during rat estrous cycle 2) if estradiol itself directly modulates the ER mRNA levels in cultured rat anterior pituitary using RT-PCR method. In rats with 4 day estrous cycle, the ER mRNA levels in anterior pituitary gland reached to maximum at proestrus 11:00h just before serum estradiol concentration showed the highest. From then, the ER mRNA levels gradually declined during the rest of the proestrus. On the other hands, in cultured rat anterior pituitary cells, the ER mRNA levels were significantly decreased by the treatment of estradiol. These results indicate that the surge of estradiol was proceeded by the increase in pituitary ER mRNA levels during the proestrus and in cultured anterior pituitary cells, estrogen might be involved in the down-regulation of the ER mRNA levels.

Mechanism of decrease in heart rate by peripheral dopaminergic D2-receptors

We performed this study in order to verify the heart rate decrease caused by the D2-receptor on cardiac sympathetic nerve endings and its relation to the concentration of norepinephrine in synaptic clefts. Sprague-Dawley rats were pithed and the heart rate was increased either by electrical stimulation of the cardiac accelerator nerve or by intravenous infusion of norepinephrine, tyramine, or isoproterenol. Increased heart rate by electrical stimulation of cardiac accelerator nerve was dose-dependently lowered by lisuride and its effect was blocked by pretreatment with sulpiride but not with yohimbine and SCH 23390. Also, the heart rate was decreased in a dose-dependent manner by clonidine and this effect was blocked by pretreatment with yohimbine, but not with sulpiride. For increased heart rate by infusion of norepinephrine, tyramine, or isoproterenol, the heart rate lowering effect of lisuride was more marked in the norepinephrine-and tyramine-infusion groups, in which the intrasynaptic concentration of norepinephrine was elevated, compared to the isoproterenol-infusion group, in which intrasynaptic concentration of norepinephrine was not elevated. In conclusion, there is a D2-receptor on the cardiac sympathetic nerve endings which decreases the heart rate and is different from the presynaptic alpha 2-receptor. Also, the heart rate lowering effect via stimulation of the D2-receptor by lisuride was more marked with increased concentration of norepinephrine in the synaptic cleft.