5-Hydroxytryptamine receptors, especially the 5-HT4 receptor, in guinea pig urinary bladder.
The function of 5-hydroxytryptamine (5-HT) receptors, especially the 5-HT4 receptor, in the urinary bladder were examined in preparations isolated from the guinea pig by in vitro receptor autoradiography and determinations of mechanical activity and acetylcholine (ACh) release. Specific [125I]SB207710 binding sites were detected evenly throughout the urinary bladder. 5-HT (3 x 10(-8)-10(-4) M) caused contractions of strips of the urinary bladder, in a concentration dependent manner. Ketanserin antagonized the 5-HT-induced contractions, while granisetron and SB204070 antagonized the contractions induced by high concentrations of 5-HT. Atropine inhibited the contractions induced by high concentrations of 5-HT. Ketanserin prevented the 5-HT-induced contractions in the presence of atropine, but granisetron and SB204070 did not affect the contractions under such a condition. 5-HT enhanced the electrically-stimulated (5 Hz, 0.5 ms) outflow of [3H]acetylcholine from strips preloaded with [3H]choline, and the enhancement was antagonized by granisetron and SB204070. Thus, the contractile response to 5-HT was mediated by activations of 5-HT2, 5-HT3 and 5-HT4 receptors. The 5-HT2 receptor may be a property of high affinity to 5-HT and located on the smooth muscle cells. The 5-HT4 as well as 5-HT3 receptor may be a property of low affinity to 5-HT and located on the cholinergic neurons.
Yoshida
Akira
A
Department of Rehabilitation and Physical Medicine, Faculty of Medicine, Kagoshima University, Japan.
S-Yamashita
Yasuko
Y
Kaibara
Muneshige
M
Taniyama
Kohtaro
K
Tanaka
Nobuyuki
N
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D011985:Receptors, Serotonin / Q000737:chemistry / Q000502:physiology*; D044422:Receptors, Serotonin, 5-HT4; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D001743:Urinary Bladder / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D044422:Receptors, Serotonin, 5-HT4; D012701:Serotonin