Cation current activated by hyperpolarization (IH) in guinea pig enteric neurons.
Intracellular microelectrode and whole cell patch-clamp recordings were made from guinea pig enteric neurons in vitro. In most myenteric AH neurons (but not S neurons), step hyperpolarizations from the resting potential evoked an inward current (IH). IH peaked in approximately 400 ms (at 36 degrees C), was fully activated at -100 mV, and did not inactivate during 10 s. IH was associated with a conductance increase and reversed polarity at about -40 mV (by extrapolation). IH was reduced in low-sodium concentrations and increased when the concentration of extracellular potassium ions was increased. Cesium (2 mM) blocked IH in a voltage-dependent manner; this led to an increase in the amplitude of the spike after-hyperpolarization. Cobalt (2-4 mM) or barium (0.01-1 mM) did not alter IH. Only 12% of submucous plexus neurons showed IH and this subgroup included both S and AH neurons. In myenteric AH neurons, IH would act in opposition to the persistent calcium-activated potassium current and thus stabilize the resting potential.
Galligan
J J
JJ
Vollum Institute, Oregon Health Sciences University, Portland 97201.
Tatsumi
H
H
Shen
K Z
KZ
Surprenant
A
A
North
R A
RA
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002586:Cesium / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D004553:Electric Conductivity; D007082:Ileum / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D009197:Myenteric Plexus / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D011817:Rabbits; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D002586:Cesium; D003035:Cobalt; D013779:Tetrodotoxin