Involvement of KCNQ2 subunits in [3H]dopamine release triggered by depolarization and pre-synaptic muscarinic receptor activation from rat striatal synaptosomes.
KCNQ2 and KCNQ3 subunits encode for the muscarinic-regulated current (I(KM)), a sub-threshold voltage-dependent K+ current regulating neuronal excitability. In this study, we have investigated the involvement of I(KM) in dopamine (DA) release from rat striatal synaptosomes evoked by elevated extracellular K+ concentrations ([K+]e) and by muscarinic receptor activation. [3H]dopamine ([3H]DA) release triggered by 9 mmol/L [K+]e was inhibited by the I(KM) activator retigabine (0.01-30 micromol/L; Emax = 54.80 +/- 3.85%; IC50 = 0.50 +/- 0.36 micromol/L). The I(KM) blockers tetraethylammonium (0.1-3 mmol/L) and XE-991 (0.1-30 micromol/L) enhanced K+-evoked [3H]DA release and prevented retigabine-induced inhibition of depolarization-evoked [3H]DA release. Retigabine-induced inhibition of K+-evoked [3H]DA release was also abolished by synaptosomal entrapment of blocking anti-KCNQ2 polyclonal antibodies, an effect prevented by antibody pre-absorption with the KCNQ2 immunizing peptide. Furthermore, the cholinergic agonist oxotremorine (OXO) (1-300 micromol/L) potentiated 9 mmol/L [K+]e-evoked [3H]DA release (Emax = 155 +/- 9.50%; EC50 = 25 +/- 1.80 micromol/L). OXO (100 micromol/L)-induced [3H]DA release enhancement was competitively inhibited by pirenzepine (1-10 nmol/L) and abolished by the M3-preferring antagonist 4-diphenylacetoxy N-methylpiperidine methiodide (1 micromol/L), but was unaffected by the M1-selective antagonist MT-7 (10-100 nmol/L) or by Pertussis toxin (1.5-3 microg/mL), which uncouples M2- and M4-mediated responses. Finally, OXO-induced potentiation of depolarization-induced [3H]DA release was not additive to that produced by XE-991 (10 micromol/L), was unaffected by retigabine (10 micromol/L), and was abolished by synaptosomal entrapment of anti-KCNQ2 antibodies. Collectively, these findings indicate that, in rat striatal nerve endings, I(KM) channels containing KCNQ2 subunits regulate depolarization-induced DA release and that I(KM) suppression is involved in the reinforcement of depolarization-induced DA release triggered by the activation of pre-synaptic muscarinic heteroreceptors.
Martire
Maria
M
Institute of Pharmacology, School of Medicine, Catholic University of S. Heart, Rome, Italy.
D'Amico
Monia
M
Panza
Elisabetta
E
Miceli
Francesco
F
Viggiano
Davide
D
Lavergata
Francesco
F
Iannotti
Fabio Arturo
FA
Barrese
Vincenzo
V
Preziosi
Paolo
P
Annunziato
Lucio
L
Taglialatela
Maurizio
M
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002219:Carbamates / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D004298:Dopamine / Q000378:metabolism*; D004594:Electrophysiology; D005455:Fluorescent Antibody Technique; D051658:KCNQ2 Potassium Channel / Q000378:metabolism*; D051659:KCNQ3 Potassium Channel / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D017072:Neostriatum / Q000378:metabolism*; D009411:Nerve Endings / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010655:Phenylenediamines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000378:metabolism*; D017661:Receptors, Presynaptic / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism*
D002219:Carbamates; D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; C496915:Kcnq2 protein, rat; C496918:Kcnq3 protein, rat; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D010655:Phenylenediamines; D011976:Receptors, Muscarinic; D017661:Receptors, Presynaptic; C101866:ezogabine; D004298:Dopamine