Investigation of PKC isoform-specific translocation and targeting of the current of the late afterhyperpolarizing potential of myenteric AH neurons.
AH neurons in the enteric nervous system play an essential role in initiating intestinal reflexes and factors that control AH neuron excitability therefore influence the state of the digestive system. Prominent afterhyperpolarizations that follow action potentials in these neurons strongly affect their excitability. In the present work, we have investigated the regulation of the afterhyperpolarizing current (I(AHP)) by protein kinase C (PKC). Electrophysiological responses and protein translocation were investigated in AH neurons of freshly dissected preparations of myenteric ganglia from the guinea-pig ileum. The activator of conventional and novel PKCs, phorbol dibutyrate, but not the activator of novel PKCs, ingenol, blocked the I(AHP). Phorbol dibutyrate had no effect on the hyperpolarization-activated current (I(h)) or on the A current (I(A)). Stimulation of synaptic inputs to the neurons also reduced the I(AHP), and had no effect on I(h) or I(A). Phorbol dibutyrate also reduced a background outward current that was present after the I(AHP) current had been blocked by clotrimazole. Both phorbol dibutyrate and ingenol caused translocation of the novel PKC, PKCepsilon, in these neurons. Only phorbol dibutyrate caused translocation of PKCgamma, a conventional PKC. The studies thus indicate that the activation of PKC by phorbol esters and by nerve stimulation affects AH neurons in a similar way, and that PKC activation targets both the I(AHP) and another background K(+) current. The I(AHP) is targeted by a conventional PKC, suggested to be PKCgamma, as this is the only conventional PKC that is prominent in AH neurons.
Nguyen
Trung V
TV
Department of Anatomy & Cell Biology and Centre for Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia.
Poole
Daniel P
DP
Harvey
John R
JR
Stebbing
Martin J
MJ
Furness
John B
JB
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D064026:Calbindins; D003022:Clotrimazole / Q000494:pharmacology; D004224:Diterpenes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006131:Growth Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D007150:Immunohistochemistry / Q000379:methods; D066298:In Vitro Techniques; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D009197:Myenteric Plexus / Q000166:cytology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D010455:Peptides / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013997:Time Factors
D064026:Calbindins; D004224:Diterpenes; D006131:Growth Inhibitors; D010455:Peptides; D010703:Phorbol Esters; D020033:Protein Isoforms; D064030:S100 Calcium Binding Protein G; C011875:ingenol dibenzoate; D011493:Protein Kinase C; D003022:Clotrimazole