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Muscarine modulation by a G‐protein alpha‐subunit of delayed rectifier K+ current in rat ventromedial hypothalamic neurones.
Author(s) -
ffrenchMullen J M,
PlataSalamán C R,
Buckley N J,
Danks P
Publication year - 1994
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1994.sp019998
Subject(s) - carbachol , endocrinology , medicine , muscarinic acetylcholine receptor , g protein , pirenzepine , muscarine , pertussis toxin , chemistry , biology , receptor , stimulation
1. Rat cultured ventromedial hypothalamic (VMH) neurones obtained from embryonic hypothalamus were used to study the muscarinic (carbachol) modulation of voltage‐gated K+ currents with the whole‐cell patch‐clamp technique. 2. Carbachol produced a potent and concentration‐dependent (100 fM to 100 microM) decrease of the outward delayed rectifier K+ current (IK) with an IC50 of 44 pM and a Hill coefficient of 0.4. The carbachol‐induced depression of IK was reduced by pirenzepine (1‐10 microM) and atropine (1 microM). Carbachol had no effect on the transient outward K+ current (IA). 3. Intracellular dialysis with guanosine 5'‐O‐(2‐thiodiophosphate) (GDP‐beta‐S, 500 microM) significantly diminished the carbachol‐induced depression of IK, suggesting GTP‐binding protein (G‐protein) involvement. Pre‐incubation of VMH neurones with pertussis toxin (200‐400 ng ml‐1) or cholera toxin (1 microgram ml‐1) for 24‐48 h had no effect on the carbachol‐induced depression of IK. This suggested that the G alpha o, G alpha i, and G alpha s G‐protein alpha‐subunits were not involved in mediating the carbachol‐induced depression of IK in VMH neurones. 4. Treatment (24‐48 h) of VMH neurones with antisense phosphothio‐oligodeoxynucleotides to the G alpha 11 G‐protein subunit (10 microM) significantly diminished the carbachol‐induced depression of IK. Treatment with 10 microM of either G alpha 11 sense or antisense to G alpha q had no effect. 5. These results demonstrate a novel and potent muscarinic depression of IK in VMN neurones, and that this depression is specifically mediated by the G alpha 11 G‐protein subunit.(ABSTRACT TRUNCATED AT 250 WORDS)