Rat GnRH neurons exhibit large conductance voltage- and Ca2+-Activated K+ (BK) currents and express BK channel mRNAs.
Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for the central regulation of reproduction. As in other neurons, the discharge pattern of action potentials is important for these neurons to function properly. Therefore it is important to elucidate the expression patterns of various types of ion channels in these neurons because they determine cell excitability. To date, voltage-gated Ca2+ channels and SK channels have been reported to be expressed in rat GnRH neurons. In this study, we focused on K+ channels and analyzed their expression in primary cultured GnRH neurons, prepared from GnRH-EGFP transgenic rats, by means of perforated patch-clamp recordings. GnRH neurons exhibited delayed-rectifier K+ currents and large conductance voltage- and Ca2+-activated K+ (BK) currents. Moreover, multicell RT-PCR (reverse transcriptase-polymerase chain reaction) experiments revealed the expression of BK channel mRNAs (alpha, beta1, beta2, and beta4). The results show the presence of delayed-rectifier K+ currents and BK currents besides previously reported slow afterhyperpolarization currents. These currents control the action potential repolarization and probably also the firing pattern, thereby regulating the cell excitability of GnRH neurons.
Hiraizumi
Yoshie
Y
Department of Physiology, Nippon Medical School, Tokyo, Japan.
Nishimura
Ichiro
I
Ishii
Hirotaka
H
Tanaka
Nobuyuki
N
Takeshita
Toshiyuki
T
Sakuma
Yasuo
Y
Kato
Masakatsu
M
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D051668:Delayed Rectifier Potassium Channels / Q000502:physiology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000502:physiology; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000502:physiology; D008297:Male; D009419:Nerve Tissue Proteins / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000502:physiology
D002121:Calcium Channel Blockers; D051668:Delayed Rectifier Potassium Channels; C494842:Kcnma1 protein, rat; C485821:Kcnmb4 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D009419:Nerve Tissue Proteins; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D051640:Small-Conductance Calcium-Activated Potassium Channels; D002104:Cadmium; D018999:Charybdotoxin; D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone; D009532:Nickel; D011188:Potassium; D002118:Calcium