Synaptic transmission induces transient Ca2+ concentration changes in cultured myenteric neurones.
The enteric nervous system controls most of the gastrointestinal functions. We applied confocal microscopy and the Ca2+ indicator Fluo-3 as an optical approach to study synaptic activation in cultures of myenteric neurones. The optical recording of [Ca2+]i (the intracellular Ca2+ concentration) was used to monitor activation, since [Ca2+]i is crucial in the coupling between neuronal excitation and the activation of several intracellular events. Extracellular fibre tract stimulation (2 s, 30 Hz) caused a transient [Ca2+]i rise in a subset of neurones (50%). These transients lasted for 5.2 s (n=36), with an average amplitude of 3.4 +/- 1.3 times the basal concentration. The removal of extracellular Ca2+ (n=15) or the application of 10-6 M tetrodotoxin (n=16) blocked this response. The N-type Ca2+-channel blocker omega-conotoxin (5 x 10 -7M) abolished the [Ca2+]i increase, while blockade of L-type and P/Q type Ca2+ channels had no effect. Single stimuli evoked a [Ca2+]i rise in the processes. omega-conotoxin-sensitive postsynaptic events required repetitive stimulation. Cholinergic blockade did not inhibit the [Ca2+]i rise in all neurones, suggesting that, besides acetylcholine, other neurotransmitters are involved. Optical imaging of [Ca2+]i can be used to study synaptic spread of activation in enteric neuronal circuits expressed in culture.
Vanden Berghe
P
P
Center for Gastroenterological Research, Catholic University Leuven, Belgium.
Tack
J
J
Coulie
B
B
Andrioli
A
A
Bellon
E
E
Janssens
J
J
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000145:classification / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D018680:Cholinergic Antagonists / Q000494:pharmacology; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006168:Guinea Pigs; D018738:Hexamethonium / Q000494:pharmacology; D018613:Microscopy, Confocal; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D010276:Parasympatholytics / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D020960:omega-Conotoxins / Q000494:pharmacology
D002121:Calcium Channel Blockers; D018680:Cholinergic Antagonists; D018733:Nicotinic Antagonists; D010276:Parasympatholytics; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D020960:omega-Conotoxins; D018738:Hexamethonium; D013779:Tetrodotoxin; D001285:Atropine; C078452:ziconotide; D009543:Nifedipine; D011188:Potassium