Single-cell RT-PCR and functional characterization of Ca2+ channels in motoneurons of the rat facial nucleus.
Voltage-dependent Ca2+ channels are a major pathway for Ca2+ entry in neurons. We have studied the electrophysiological, pharmacological, and molecular properties of voltage-gated Ca2+ channels in motoneurons of the rat facial nucleus in slices of the brainstem. Most facial motoneurons express both low voltage-activated (LVA) and high voltage-activated (HVA) Ca2+ channel currents. The HVA current is composed of a number of pharmacologically separable components, including 30% of N-type and approximately 5% of L-type. Despite the dominating role of P-type Ca2+ channels in transmitter release at facial motoneuron terminals described in previous studies, these channels were not present in the cell body. Remarkably, most of the HVA current was carried through a new type of Ca2+ channel that is resistant to toxin and dihydropyridine block but distinct from the R-type currents described in other neurons. Using reverse transcription followed by PCR amplification (RT-PCR) with a powerful set of primers designed to amplify all HVA subtypes of the alpha1-subunit, we identified a highly heterogeneous expression pattern of Ca2+ channel alpha1-subunit mRNA in individual neurons consistent with the Ca2+ current components found in the cell bodies and axon terminals. We detected mRNA for alpha1A in 86% of neurons, alpha1B in 59%, alpha1C in 18%, alpha1D in 18%, and alpha1E in 59%. Either alpha1A or alpha1B mRNAs (or both) were present in all neurons, together with various other alpha1-subunit mRNAs. The most frequently occurring combination was alpha1A with alpha1B and alpha1E. Taken together, these results demonstrate that the Ca2+ channel pattern found in facial motoneurons is highly distinct from that found in other brainstem motoneurons.
Plant
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Physiologisches Institut, Universität des Saarlandes, 66421 Homburg, Germany.
Schirra
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Katz
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Uchitel
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Konnerth
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A
D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000166:cytology; D002104:Cadmium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics*; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D004095:Dihydropyridines / Q000494:pharmacology; D005154:Facial Nerve / Q000737:chemistry / Q000166:cytology*; D015640:Ion Channel Gating / Q000187:drug effects; D009046:Motor Neurons / Q000737:chemistry*; D009532:Nickel / Q000494:pharmacology; D009568:Nitrendipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D011950:Receptors, Cholinergic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013111:Spider Venoms / Q000494:pharmacology; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D004095:Dihydropyridines; D010455:Peptides; D012333:RNA, Messenger; D011950:Receptors, Cholinergic; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; D002104:Cadmium; C075851:omega-conotoxin-MVIIC; D009532:Nickel; D020866:omega-Conotoxin GVIA; D009568:Nitrendipine