Electrical and synaptic properties of embryonic luteinizing hormone-releasing hormone neurons in explant cultures.
Voltage- and ligand-activated channels in embryonic neurons containing luteinizing hormone-releasing hormone (LHRH) were studied by patch-pipette, whole-cell current and voltage clamp techniques. LHRH neurons were maintained in explant cultures derived from olfactory pit regions of embryonic mice. Cells were marked intracellularly with Lucifer yellow following recording. Sixty-two cells were unequivocally identified as LHRH neurons by Lucifer yellow and LHRH immunocytochemistry. The cultured LHRH neurons had resting potentials around -50 mV, exhibited spontaneous discharges generated by intrinsic and/or synaptic activities and contained a time-dependent inward rectifier (Iir). Voltage clamp analysis of ionic currents in the LHRH neuron soma revealed a tetrodotoxin-sensitive Na+ current (INa) and two major types of K+ currents, a transient current (IA), a delayed rectifier current (IK) and low- and high-voltage-activated Ca2+ currents. Spontaneous depolarizing synaptic potentials and depolarizations induced by direct application of gamma-aminobutyrate were both inhibited by picrotoxin or bicuculline, demonstrating the presence of functional gamma-aminobutyrate type A synapses on these neurons. Responses to glutamate were found in LHRH neurons in older cultures. Thus, embryonic LHRH neurons not yet positioned in their postnatal environment in the forebrain contained a highly differentiated repertoire of voltage- and ligand-gated channels.
Kusano
K
K
Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Fueshko
S
S
Gainer
H
H
Wray
S
S
D000200:Action Potentials; D000818:Animals; D015220:Calcium Channels / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000196:embryology / Q000378:metabolism / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D010852:Picrotoxin / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D015220:Calcium Channels; D007987:Gonadotropin-Releasing Hormone; D007473:Ion Channels; D010852:Picrotoxin; D011803:Quinine; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid