Evidence for adenosine triphosphate (ATP) as an excitatory neurotransmitter in guinea-pig gastric antrum.
- Author:
Tong Mook KANG
1
;
Wenxie XU
;
Sung Joon KIM
;
Seung Cheol AHN
;
Young Chul KIM
;
Insuk SO
;
Myoung Kyu PARK
;
Dae Yong UHM
;
Ki Whan KIM
Author Information
1. Department of Physiology and Biophysics, Seoul National University College of Medicine, Seoul, South Korea.
- Publication Type:Original Article
- Keywords:
ATP;
Smooth musle;
Purinoceptors;
Stomach
- MeSH:
Adenosine Triphosphate*;
Adenosine*;
Atropine;
Baths;
Guanethidine;
Indomethacin;
Membranes;
Muscle, Smooth;
Neurotransmitter Agents*;
Pyloric Antrum*;
Receptors, Purinergic;
Relaxation;
Stomach;
Suramin;
Uridine Triphosphate
- From:The Korean Journal of Physiology and Pharmacology
1999;3(2):165-174
- CountryRepublic of Korea
- Language:English
-
Abstract:
We explore the question of whether adenosine 5'-triphosphate (ATP) acts as an excitatory neurotransmitter in guinea-pig gastric smooth muscle. In an organ bath system, isometric force of the circular smooth muscle of guinea-pig gastric antrum was measured in the presence of atropine and guanethidine. Under electrical field stimulation (EFS) at high frequencies (>20 Hz), NO-mediated relaxation during EFS was followed by a strong contraction after the cessation of EFS (a "rebound-contraction"). Exogenous ATP mimicked the rebound-contraction. A known P2Y-purinoceptor antagonist, reactive blue 2 (RB-2), blocked the rebound-contraction while selective desensitization of P2x-purinoceptor with alpha, beta-MeATP did not affect it. ATP and 2-MeSATP induced smooth muscle contraction, which was effectively blocked by RB-2 and suramin, a nonselective P2-purinoceptor antagonist. Particularly, in the presence of RB-2, exogenous ATP and 2-MeSATP inhibited spontaneous phasic contractions, suggestingthe existence of different populations of purinoceptors. Both the rebound-contraction and the agonist-induced contraction were not inhibited by indomethacin. The rank orders of agonists' potency were 2-MeSATP > ATP gtoreq UTP for contraction and alpha, beta-MeATP gtoreq beta, gamma-MeATP for inhibition of the phasic contraction, that accord with the commonly accepted rank order of the classical P2Y-purinoceptor subtypes. Electrical activities of smooth muscles were only slightly influenced by ATP and 2-MeSATP, whereas alpha, beta-MeATP attenuated slow waves with membrane hyperpolarization. From the above results, it is suggested that ATP acts as an excitatory neurotransmitter, which mediates the rebound-contraction via P2Y-purinoceptor in guinea-pig gastric antrum.
