Histamine suppresses A-type potassium current in myenteric neurons from guinea pig small intestine.
Perforated patch-clamp methods for recording ionic currents in the whole-cell configuration were used to test the hypothesis that the ionic mechanisms for the excitatory actions of histamine on enteric neurons include suppression of A-type K(+) current (I(A)). Histamine and the selective histamine H(2) receptor agonist, dimaprit, reduced the amplitude of I(A) without affecting the slope factor for I(A) steady-state inactivation curves. Suppression of I(A) was restricted to after hyperpolarization-type myenteric neurons that were immunoreactive for calbindin. The selective histamine H(2) receptor antagonist cimetidine suppressed the action of histamine and dimaprit. Elevation of intraneuronal cAMP by forskolin, a membrane-permeant analog of cAMP, and treatment with a phosphodiesterase inhibitor suppressed I(A.) The results are consistent with the hypothesis that suppression of I(A) is part of the ionic mechanism responsible for elevation of excitability during both slow synaptic excitation and slow synaptic excitation-like responses evoked by paracrine mediators, such as histamine, in after hyperpolarization-type myenteric neurons.
Starodub
A M
AM
Department of Physiology and Cell Biology, College of Medicine and Public Health, The Ohio State University, Columbus 43211-1218, USA.
Wood
J D
JD
D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017259:Dimaprit / Q000494:pharmacology; D004347:Drug Interactions; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D017442:Histamine Agonists / Q000494:pharmacology; D006633:Histamine Antagonists / Q000494:pharmacology; D007421:Intestine, Small / Q000187:drug effects / Q000294:innervation*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000502:physiology
D017442:Histamine Agonists; D006633:Histamine Antagonists; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011970:Receptors, Histamine H2; D002927:Cimetidine; D006632:Histamine; D000242:Cyclic AMP; D017259:Dimaprit