Keiko Takemura (1), Kohei Takada (1,2), Shunichi Mameya (1), Muneshige
Kaibara (1) and Kohtaro Taniyama (1,*)
(1) Department of Pharmacology, Nagasaki University School of Medicine,
Nagasaki 852-8523 Japan
(2) Department of Surgery II, Kansai Medical University, Moriguchi 570-8506,
Japan
(*) To whom correspondence should be addressed.
Abstract: Functions and the presence of 5-hydroxytryptamine (5-HT)
receptors in the fundus, corpus and antrum of the guinea pig stomach were
examined by measuring contractile force and acetylcholine (ACh) release.
Stimulation of the 5-HT1 receptor caused tetrodotoxin (TTX)-insensitive
relaxations in the preparations from 3 regions. Stimulation of the 5-HT2
receptor caused TTX-insensitive contractions in the preparations of fundus
and antrum. Stimulation of 5-HT3 receptors caused contractions
that were sensitive to TTX and atropine and enhanced the outflow of [3H]ACh
from preparations of only antrum. Stimulation of 5-HT4 receptors
caused contractions of antral strips and decreased relaxations of corporal
strips and enhanced the outflow of [3H]ACh from the preparations
of both corpus and antrum. In the guinea pig stomach, the fundus possesses
relaxant 5-HT1 receptor < contractile 5-HT2 receptors
and caused the contractile response to 5-HT. The corpus possesses relaxant
5-HT1 receptors and relaxant receptors other than 5-HT1,
5-HT2, 5-HT3 and 5-HT4 receptors > contractile
5-HT4 receptor, and therefore 5-HT caused relaxations. The antrum
possesses relaxant 5-HT1 receptor < contractile 5-HT2,
5-HT3 and 5-HT4 receptors, and thus 5-HT caused contractions.
Keywords: Stomach fundus, Stomach corpus, Stomach antrum, Acetylcholine
release, Contractile response