Galligan J J, Tatsumi H, Shen K Z, Surprenant A, North R A
Vollum Institute, Oregon Health Sciences University, Portland 97201.
Am J Physiol. 1990 Dec;259(6 Pt 1):G966-72. doi: 10.1152/ajpgi.1990.259.6.G966.
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.
