Potassium channels opened by noradrenaline and other transmitters in excised membrane patches of guinea-pig submucosal neurones.
AUTOR(ES)
Shen, K Z
RESUMO
1. Unitary potassium currents were recorded in outside-out patches of membrane from guinea-pig submucosal neurones. The actions of alpha 2-adrenoceptor agonists, somatostatin and [Met5]enkephalin were studied. 2. Three main groups of background potassium channels were active. At -70 mV with 160 mM-potassium on both sides of the membrane, they had conductances of 30-65 (small), 120-160 (intermediate) and 220-260 pS (large). 3. The open channel current-voltage relation showed only constant-field rectification. Extracellular barium (2 mM) and caesium (2 mM) decreased inward but not outward currents. Tetraethylammonium (10 mM) had no effect. 4. Noradrenaline, somatostatin and [Met5]enkephalin each increased the open probability of all three classes of channel when two or more unitary amplitude channels were active in the membrane patch. Agonists were ineffective when no channel, or a single channel, was discernible in the patch. Agonists did not cause the appearance of unitary currents distinct from those seen prior to their application. 5. The effect of the agonists required intracellular guanosine 5'-triphosphate. 6. The results show that the hyperpolarization of submucosal plexus neurones by noradrenaline, somatostatin and [Met5]enkephalin results from the increased opening of at least three types of background potassium channel, and that the coupling from the receptors to the channels is maintained in excised membrane patches.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1179999Documentos Relacionados
- Common ionic mechanisms of excitation by substance P and other transmitters in guinea-pig submucosal neurones.
- Inhibition of calcium currents by noradrenaline, somatostatin and opioids in guinea-pig submucosal neurones.
- Adenosine 5'-triphosphate modulates membrane potassium conductance in guinea-pig myenteric neurones.
- Somatostatin-mediated inhibitory postsynaptic potential in sympathetically denervated guinea-pig submucosal neurones.
- Muscarinic agonists inactivate potassium conductance of guinea-pig myenteric neurones.