| Project/Area Number |
61480076
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
畜産学(含草地学)
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| Research Institution | Nagoya University |
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Principal Investigator |
YOKOYAMA Akira Nagoya University, School of Agriculture, 農学部, 教授 (50023388)
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| Co-Investigator(Kenkyū-buntansha) |
MAEDA Kei-ichiro Nagoya University, School of Agriculture, 農学部, 助手 (30181580)
TOMOGANE Hiroshi Nagoya University, School of Agriculture, 農学部, 助手 (30023493)
OTA Katuski Nagoya University, School of Agriculture, 農学部, 助教授 (00023424)
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| Project Period (FY) |
1986 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥5,900,000 (Direct Cost: ¥5,900,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1986: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | Hypothalamus / LH / Oxytocin / Pulsatile secretion / Rat / Suckling stimulus / Surge / オキシトシン / 乳腺神経 / プロラクチン / コルチコイド / 下垂体 / 栄養制御 |
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| Research Abstract |
The suckling stimulus has been reported to be a dominant factor suppressing LH secretion during lactation. The suckling stimulus could change with the advancement of lactation or physiologcal condition of mothers e.g. number of pups the degree of pups development. We, first, studied whether or not the electrical stimulation of the mammary nerve could be used as a substitute for the suckling sitmulus, and secondly, we studied effects of thesuckling sitmulus on the secretory pattern of lh in ovariectomized lactating rats throughout the lactating peruid.
1. The electrical sitmulation of not only the mammary nerve but also the saphoenous and median nerves increased the plasme oxytocin concentration. Although chlorpromazine adminidtration was able to inhibit the increase of plasma oxytocin level in response to the immobilization stress, chlorpromazine administration failed to prevent the increase occurring after the electrical stimulation of the mammary, saphenous and median nerves. No incre
… More
ase in the plasma oxytocin levels when the mother was placed with pups whose mouths were sealed not to suckle the teat. Further studies are required to discriminate the oxytocin response to the electrical stimulation of the mammary nerve from that to the sitmulation of the median and saphenous nerves.
2. Pulsatile LH secretion was strongly suppressed on either day 10 or 20 of lactation in intact rats in which the base line of plasma LH was kept very low. In ovariectomized rats the base line was kept as low as that observed in intact rats on day 10 day 20 the base line raised and pulsatile secretion appeared in 5 out of 6 ovraiectomized lactating rats. Daily LH surges occurred in the late afternoon in both lactating rats inplanted with estradiol on day 6 or 15. The mean LH level and the frequency and amplitude of LH pulses gradually increased after removal of pups on day 8 of lactation. In cycling rats the frequency of LH pulses was unchanged after ovariectomy, although the mean LH level and the amplitude of LH pulses increased. These results clearly indicate: 1. Suppression of pulsatile LH secretion by the suckling stimulus at the hypothalamo-pituitary level is removed in late lactation. 2. The mechanisms responsible for the estradiol induced LH surge are not impaired by the sucklig sitmulus. 3. The suckling sitmulus suppresses pulsatile secretion in a different manner from that of ovarian steroids. Less
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