Authors: T Maeda H Ikegami M Sakata M Yamaguchi K Wada K Koike K Adachi H Kurachi K Hirota A Miyake
Publish Date: 2014/04/04
Volume: 19, Issue: 9, Pages: 586-592
Abstract
The effect of estradiol E2 on rat tuberoinfundibular dopaminergic TIDA neurons was examined in vivo employing chronic intraventricular icv infusion technique using an osmotic minipump The activity of TIDA neurons was assessed by the release and synthesis of prolactin PRL in the rat pituitary gland and by the changes in the 3 4dihydroxyphenylacetic acid DOPAC and dopamine DA levels and in the DOPAC/DA ratio in the rat hypothalamus We also examined the 3H E2 binding in the rat hypothalamus Ovariectomized female Wistar rats with E2 replacement were treated with daily icv infusion of 1μM of E2 or saline vehicle for 1 3 and 7 days using the Alzet osmotic minipump and brain infusion kit At 1 day of icv infusion of E2 the serum PRL level was significantly decreased compared with that in the vehicle group Northern blot analysis of the total RNA isolated from the pituitary glands demonstrated a decrease in the PRL gene transcript level in the E2 group At 3 days of E2 treatment however the serum PRL level was significantly increased compared with that of the vehicleinjected group and Northern blot analysis also demonstrated that the PRL gene transcript level was increased in the E2 group At 7 days of E2 administration there were no significant differences between the E2 and vehicle groups in either serum PRL or PRL gene transcript levels There was a significant increase in the DOPAC/DA ratio after 1 day in the E2 group However no significant effects of E2 on this ratio were observed at 3 and 7 days of treatment The DOPAC concentration in the E2 group was significantly increased at day 1 and significantly decreased at day 3 compared with that of the respective time in vehicle group At day 7 there was no significant change in DOPAC concentration in either groups The DA concentrations in the hypothalamus was not changed on any day in either group Specific 3H E2 binding was observed in the rat hypothalamus These data suggest that E2 may have a biphasic effect on the accumulation of PRL gene transcripts and on the PRL secretion in the rat pituitary by first stimulating and then inhibiting the TIDA neuronal activity
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