Histamine H(2) receptor activated chloride conductance in myenteric neurons from guinea pig small intestine.
J Neurophysiol
; 83(4): 1809-16, 2000 Apr.
Article
in En
| MEDLINE
| ID: mdl-10758093
ABSTRACT
Whole cell perforated patch-clamp methods were used to investigate ionic mechanisms underlying histamine-evoked excitatory responses in small intestinal AH-type myenteric neurons. When physiological concentrations of Na(+), Ca(2+), and Cl(-) were in the bathing medium, application of histamine significantly increased total conductance as determined by stepping to 50 mV from a holding potential of -30 mV. The current reversed at a membrane potential of -30 +/- 5 (SE) mV and current-voltage relations exhibited outward rectification. The reversal potential for the histamine-activated current was unchanged by removal of Na(+) and Ca(2+) from the bathing medium. Reduction of Cl(-) from 155 mM to 55 mM suppressed the current when the neurons were in solutions with depleted Na(+) and Ca(2+). Current-voltage curves in solutions with reduced Cl(-) were linear and the reversal potential was changed from -30 +/- 5 mV to 7 +/- 4 mV. Niflumic acid, but not anthracene-9-carboxylic acid (9-AC) nor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), suppressed the histamine-activated current. A membrane permeable analogue of cAMP evoked currents similar to those activated by histamine. A selective histamine H(2) receptor agonist (dimaprit) mimicked the action of histamine and a selective histamine H(2) receptor antagonist (cimetidine) blocked the conductance increase evoked by histamine. A selective adenosine A(1) receptor agonist (CCPA) reduced the histamine-activated current and a selective adenosine A(1) receptor antagonist (CPT) reversed the inhibitory action. The results suggest that histamine acts at histamine H(2) receptors to increase Cl(-) conductance in AH-type enteric neurons. Cyclic AMP appears to be a second messenger in the signal transduction process. Results with a selective adenosine A(1) receptor agonist and antagonist add to existing evidence for co-coupling of inhibitory adenosine A(1) receptors and histamine H(2) receptors to adenylate cyclase in AH-type enteric neurons.
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Database:
MEDLINE
Main subject:
Receptors, Histamine H2
/
Chlorides
/
Intestine, Small
/
Myenteric Plexus
/
Neurons
Limits:
Animals
Language:
En
Journal:
J Neurophysiol
Year:
2000
Type:
Article
Affiliation country:
United States