Bradykinin, but not muscarinic, inhibition of M-current in rat sympathetic ganglion neurons involves phospholipase C-beta 4.
Rat superior cervical ganglion (SCG) neurons express low-threshold noninactivating M-type potassium channels (I(K(M))), which can be inhibited by activation of M(1) muscarinic receptors (M(1) mAChR) and bradykinin (BK) B(2) receptors. Inhibition by the M(1) mAChR agonist oxotremorine methiodide (Oxo-M) is mediated, at least in part, by the pertussis toxin-insensitive G-protein Galpha(q) (Caulfield et al., 1994; Haley et al., 1998a), whereas BK inhibition involves Galpha(q) and/or Galpha(11) (Jones et al., 1995). Galpha(q) and Galpha(11) can stimulate phospholipase C-beta (PLC-beta), raising the possibility that PLC is involved in I(K(M)) inhibition by Oxo-M and BK. RT-PCR and antibody staining confirmed the presence of PLC-beta1, -beta2, -beta3, and -beta4 in rat SCG. We have tested the role of two PLC isoforms (PLC-beta1 and PLC-beta4) using antisense-expression constructs. Antisense constructs, consisting of the cytomegalovirus promoter driving antisense cRNA corresponding to the 3'-untranslated regions of PLC-beta1 and PLC-beta4, were injected into the nucleus of dissociated SCG neurons. Injected cells showed reduced antibody staining for the relevant PLC-beta isoform when compared to uninjected cells 48 hr later. BK inhibition of I(K(M)) was significantly reduced 48 hr after injection of the PLC-beta4, but not the PLC-beta1, antisense-encoding plasmid. Neither PLC-beta antisense altered M(1) mAChR inhibition by Oxo-M. These data support the conclusion of Cruzblanca et al. (1998) that BK, but not M(1) mAChR, inhibition of I(K(M)) involves PLC and extends this finding by indicating that PLC-beta4 is involved.
Haley
J E
JE
Wellcome Laboratory for Molecular Pharmacology, Department of Pharmacology, University College London, London, WC1E 6BT, United Kingdom.
Abogadie
F C
FC
Fernandez-Fernandez
J M
JM
Dayrell
M
M
Vallis
Y
Y
Buckley
N J
NJ
Brown
D A
DA
D000818:Animals; D001920:Bradykinin / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008845:Microinjections; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D054799:Phospholipase C beta; D010957:Plasmids; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism*
D007527:Isoenzymes; D018727:Muscarinic Antagonists; D016376:Oligonucleotides, Antisense; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012333:RNA, Messenger; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C518035:Plcb1 protein, rat; C518038:Plcb2 protein, rat; C518041:Plcb3 protein, rat; C518044:Plcb4 protein, rat; D001920:Bradykinin