We aimed to investigate the effects of serotonin (5-hydroxytryptamine, 5-HT) on the bovine ciliary muscle and subsequently to characterize and identify the subtypes of 5-HT receptors involved in the serotonin-evoked contractility muscle. The binding of [3H]ketanserin, [3H]granisetron and [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) was analyzed. All labelled compounds bound with high affinity to a single site in the membrane preparations studied. The affinity (Kd) of the binding site was 7.5±1.2 nM for [3H]ketanserin, 6.9±0.8 nM for [3H]granisetron and 4.4±0.31 nM for [3H]8-OH-DPAT. The density of receptors (Bmax) was 1062±43.0 fmol/mg protein for [3H]ketanserin, 566±2.32 fmol/mg protein for [3H]granisetron and 205±4.63 fmol/mg protein for [3H]8-OH-DPAT. The serotonin-induced contraction appeared to be competitively antagonized by ketanserin (0.1, 1 and 10 μM) and ondansetron (0.1, 10 and 100 μM) which produced a pA2 value of 8.5±0.12 and 8.0±0.19, respectively. 8-OH-DPAT and 5-carboxamidotryptamine (5-CT) proved to be completely ineffective. We conclude that serotonin induces bovine ciliary muscle contraction via 5-HT2 and 5-HT3 receptors while the 5-HT1A receptors, although present, do not mediate the contractile response.
Pharmacological characterization of the 5-HT1A, 5-HT2 and 5-HT3 receptors in the bovine ciliary muscle
LOGRANO, Marcello Diego;
2003-01-01
Abstract
We aimed to investigate the effects of serotonin (5-hydroxytryptamine, 5-HT) on the bovine ciliary muscle and subsequently to characterize and identify the subtypes of 5-HT receptors involved in the serotonin-evoked contractility muscle. The binding of [3H]ketanserin, [3H]granisetron and [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT) was analyzed. All labelled compounds bound with high affinity to a single site in the membrane preparations studied. The affinity (Kd) of the binding site was 7.5±1.2 nM for [3H]ketanserin, 6.9±0.8 nM for [3H]granisetron and 4.4±0.31 nM for [3H]8-OH-DPAT. The density of receptors (Bmax) was 1062±43.0 fmol/mg protein for [3H]ketanserin, 566±2.32 fmol/mg protein for [3H]granisetron and 205±4.63 fmol/mg protein for [3H]8-OH-DPAT. The serotonin-induced contraction appeared to be competitively antagonized by ketanserin (0.1, 1 and 10 μM) and ondansetron (0.1, 10 and 100 μM) which produced a pA2 value of 8.5±0.12 and 8.0±0.19, respectively. 8-OH-DPAT and 5-carboxamidotryptamine (5-CT) proved to be completely ineffective. We conclude that serotonin induces bovine ciliary muscle contraction via 5-HT2 and 5-HT3 receptors while the 5-HT1A receptors, although present, do not mediate the contractile response.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
