Relative contribution of SKCa and TREK1 channels in purinergic and nitrergic neuromuscular transmission in the rat colon.
Purinergic and nitrergic neurotransmission predominantly mediate inhibitory neuromuscular transmission in the rat colon. We studied the sensitivity of both purinergic and nitrergic pathways to spadin, a TWIK-related potassium channel 1 (TREK1) inhibitor, apamin, a small-conductance calcium-activated potassium channel blocker and 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ), a specific inhibitor of soluble guanylate cyclase. TREK1 expression was detected by RT-PCR in the rat colon. Patch-clamp experiments were performed on cells expressing hTREK1 channels. Spadin (1 μM) reduced currents 1) in basal conditions 2) activated by stretch, and 3) with arachidonic acid (AA; 10 μM). l-Methionine (1 mM) or l-cysteine (1 mM) did not modify currents activated by AA. Microelectrode and muscle bath studies were performed on rat colon samples. l-Methionine (2 mM), apamin (1 μM), ODQ (10 μM), and N(ω)-nitro-l-arginine (l-NNA; 1 mM) depolarized smooth muscle cells and increased motility. These effects were not observed with spadin (1 μM). Purinergic and nitrergic inhibitory junction potentials (IJP) were studied by incubating the tissue with l-NNA (1 mM) or MRS2500 (1 μM). Both purinergic and nitrergic IJP were unaffected by spadin. Apamin reduced both IJP with a different potency and maximal effect for each. ODQ concentration dependently abolished nitrergic IJP without affecting purinergic IJP. Similar effects were observed in hyperpolarizations induced by sodium nitroprusside (1 μM) and nitrergic relaxations induced by electrical stimulation. We propose a pharmacological approach to characterize the pathways and function of purinergic and nitrergic neurotransmission. Nitrergic neurotransmission, which is mediated by cyclic guanosine monophosphate, is insensitive to spadin, an effective TREK1 channel inhibitor. Both purinergic and nitrergic neurotransmission are inhibited by apamin but with different relative sensitivity.
Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Bellaterra, Spain.
V
V
Gil
D
D
Gallego
H
H
Moha Ou Maati
R
R
Peyronnet
M
M
Martínez-Cutillas
C
C
Heurteaux
M
M
Borsotto
M
M
Jiménez
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D003106:Colon / Q000502:physiology*; D003545:Cysteine / Q000494:pharmacology; D008297:Male; D008715:Methionine / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024683:Potassium Channels, Tandem Pore Domain / Q000187:drug effects / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D010069:Oxadiazoles; D010455:Peptides; D026902:Potassium Channel Blockers; D024683:Potassium Channels, Tandem Pore Domain; D011810:Quinoxalines; D051640:Small-Conductance Calcium-Activated Potassium Channels; C103742:potassium channel protein TREK-1; C551795:spadin peptide; D009599:Nitroprusside; D019335:Nitroarginine; D001030:Apamin; D008715:Methionine; D003545:Cysteine