Serotonin receptors expressed in Xenopus oocytes by mRNA from brain mediate a closing of K+ membrane channels.
Membrane currents evoked by serotonin (5-HT) were studied in Xenopus oocytes injected with rat brain mRNA. Intracellular EGTA was used to abolish the Ca2(+)-dependent oscillatory Cl- current to 5-HT, revealing an underlying smooth inward current. This was associated with a decreased membrane conductance, was antagonized by Ba2+ and Zn2+ (but not TEA), and probably arises through a closing of K+ channels. Half-maximal responses were obtained with 30 nM 5-HT, while 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) was ineffective. Furthermore, methysergide, mianserin and lysergic acid antagonized the K(+)-closing response to 5-HT, consistent with it being mediated through 5-HT1C receptors. The largest K(+)-closing responses were induced by a size fraction of mRNA which also induced a large K+ conductance, suggesting that the response requires expression of both receptors and K+ channels. The K(+)-closing response induced in the oocyte resembles the M- and S-type currents described in, respectively, mammalian and invertebrate neurons.
Parker
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Department of Psychobiology, University of California, Irvine 92717.
Panicker
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MM
Miledi
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D000818:Animals; D001921:Brain / Q000378:metabolism*; D005786:Gene Expression Regulation; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011985:Receptors, Serotonin / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology; D014982:Xenopus laevis
D015221:Potassium Channels; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D012701:Serotonin