Modulation of calcium currents by G-proteins and adenosine receptors in myenteric neurones cultured from adult guinea-pig small intestine.
1. Whole-cell patch clamp methods were used to analyse voltage-dependent calcium currents in cultured myenteric neurones enzymatically isolated from adult guinea-pig small intestine. 2. Activation of G-proteins by intracellular administration of GTP-gamma-S (100-200 microM in pipette) decreased the amplitude of high voltage activated Ca2+ current (ICa) by more than 50%. Residual ICa was activated more slowly and was non-inactivating during 500 ms test pulses when GTP-gamma-S was included in the pipette solution. 3. Inclusion of 500 microM GDP-beta-S in the patch pipettes increased the amplitude of ICa by over 30% without altering the voltage-dependency. 4. Extracellular application of 2-chloroadenosine suppressed ICa dose-dependently by reducing both transient and sustained components of the current. 5. Pretreatment of the neurones with cholera toxin or forskolin did not alter the actions of GTP-gamma-S or GDP-beta-S or 2-chloroadenosine. 6. The results suggest that high threshold calcium channels in myenteric neurones are influenced by G-proteins and that the inhibitory action of 2-chloroadenosine on ICa involves G-protein coupling of the adenosine receptors to the Ca2+ channel.
Baidan
L V
LV
Department of Physiology, College of Medicine, Ohio State University, Columbus 43210-1218, USA.
Zholos
A V
AV
Wood
J D
JD
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000187:drug effects*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006168:Guinea Pigs; D007421:Intestine, Small / Q000187:drug effects; D009197:Myenteric Plexus / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D013997:Time Factors
D015220:Calcium Channels; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000241:Adenosine