Blockade of Gi/o proteins modifies electrical activity of S-myenteric neurons from guinea-pig ileum.
We have investigated the effect of blockade of G(i/o) proteins on the electrical activity of S-myenteric neurons from guinea-pig ileum longitudinal muscle-myenteric plexus preparations. Intracellular recordings were made from either control or pertussis toxin (PTX) treated tissues. PTX is known to disrupt the function of G(i/o) proteins. Incubation with PTX (300 ng/ml) induced three main changes in the electrophysiological characteristics of S-neurons: (1) resting membrane potential was more depolarised; (2) fast excitatory postsynaptic potentials (EPSPs) were faster and narrower; and (3) spontaneous fast EPSPs and action potentials were more frequent. Amplitude of slow EPSPs was not modified. This general increase in excitability after blockade of G(i/o) proteins shares characteristics with the slow depolarisation induced by long-lasting trains of low-frequency electrical stimulation and could be mediated by similar mechanisms. Electrophysiological activity of S-myenteric neurons could be modulated by an inhibitory tone, which PTX could modify by either pre- or post-synaptic mechanisms, such as inhibition of the tonic release of inhibitory neurotransmitters and/or intracellular signal transduction involving PTX-sensitive G(i/o) proteins.
Abalo
R
R
Area Farmacología, Depto. Ciencias de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Avda. de Atenas s/n, 28922 Alcorcón, Madrid, Spain.
Goicoechea
C
C
Martín
M I
MI
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors* / Q000502:physiology; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009197:Myenteric Plexus / Q000166:cytology* / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D037342:Pertussis Toxin / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go