Role of Na+ and Ca2+ Channels in the Preoptic LH Surge Generating Mechanism in Proestrous Rats
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Accession number;03A0337715
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| Title;Role of Na+ and Ca2+ Channels in the Preoptic LH Surge Generating Mechanism in Proestrous Rats |
| Author;
FUKUSHIMA A
(Yokohama City Univ. School Of Medicine, Yokohama, Jpn)
SANO A
(Yokohama City Univ. School Of Medicine, Yokohama, Jpn)
AIBA S
(Yokohama City Univ. School Of Medicine, Yokohama, Jpn)
KIMURA F
(Yokohama City Univ. School Of Medicine, Yokohama, Jpn)
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Journal Title;Endocr J
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Journal Code:F0625A
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ISSN:0918-8959
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VOL.50;NO.2;PAGE.145-153(2003)
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| Figure&Table&Reference;FIG.6, REF.39 |
| Pub. Country;Japan |
| Language;English |
| Abstract;We studied whether Na+ and Ca2+ channels are involved in the neural mechanism responsible for the surge of gonadotropin-releasing hormone (GnRH) in proestrous rats. In experiment 1, female rats in proestrus were ip injected at 1345h with pentobarbital sodium (35mg/kg) to block spontaneous surge of LH and electrical stimulation was applied between 1400 and 1600h to the preoptic area (POA) together with POA injection of 0.5.MU.l saline containing the Na+ channel blocker tetrodotoxin (TTX) at a concentration of 1.MU.M, 2.MU.M, or 5.MU.M. Since 5.MU.M TTX completely-blocked the increase in serum LH concentrations evoked by the POA stimulation, we used this concentration in experiment 2 to observe the TTX effect on the spontaneous LH surge. In experiment 2, bilateral injections of 1.5.MU.l of 5.MU.M TTX at 1430h in the POA in proestrous rats postponed the peak time and reduced the peak level of the LH surge. In experiment 3, bilateral injections of 1.5.MU.l of 5.MU.M L-type Ca2+ channel blocker nifedipine at 1430h in the POA completely blocked the LH surge. Since the cell bodies of GnRH neurons are primarily concentrated in the POA in rats, these results suggest that both voltage-sensitive Na+ channels and Ca2+ channels contribute to the generation of action potentials at GnRH cell bodies for the surge release of GnRH. (author abst.) |
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