No / The effect of the selective serotonin reuptake inhibitor fluoxetine was examined on the 5-HT4 receptor-mediated relaxation in the rat isolated ileum.
Fluoxetine unsurmountably antagonized the relaxation to exogenous 5-HT with abolition of the response at 10 ¿M. Fluoxetine (10 ¿M) also caused a gradual loss of the resting tension. These effects of fluoxetine were prevented by a prior addition of the 5-HT4 receptor selective antagonist GR113808 (100 nM), which itself caused a contraction of the tissues when administered alone.
Fluoxetine (10 ¿M) also failed to prevent the relaxation due to exogenous 5-HT and the 5-HT4 receptor agonist 5-methoxytryptamine in tissues taken from the rats treated with para-chlorophenylalanine (300 mg kg¿1) for 3 and 6 days, which reduced the 5-HT level in the mucosa by 88 and 97.5% respectively.
The contraction of the tissues with GR113808 indicates the presence of an endogenous 5-HT tone at the 5-HT4 receptor in the rat ileum. It is hypothesized that in the presence of fluoxetine, the concentration of endogenous 5-HT at the receptor was increased sufficiently to reduce or abolish the relaxation to 5-HT added exogenously. The inability of fluoxetine to prevent the relaxation to 5-HT in the presence of GR113808 or after the p-CPA treatment supports this hypothesis.
The effect of the selective serotonin reuptake inhibitor fluoxetine was examined on the 5-HT4 receptor-mediated relaxation in the rat isolated ileum.
Fluoxetine unsurmountably antagonized the relaxation to exogenous 5-HT with abolition of the response at 10 ¿M. Fluoxetine (10 ¿M) also caused a gradual loss of the resting tension. These effects of fluoxetine were prevented by a prior addition of the 5-HT4 receptor selective antagonist GR113808 (100 nM), which itself caused a contraction of the tissues when administered alone.
Fluoxetine (10 ¿M) also failed to prevent the relaxation due to exogenous 5-HT and the 5-HT4 receptor agonist 5-methoxytryptamine in tissues taken from the rats treated with para-chlorophenylalanine (300 mg kg¿1) for 3 and 6 days, which reduced the 5-HT level in the mucosa by 88 and 97.5% respectively.
The contraction of the tissues with GR113808 indicates the presence of an endogenous 5-HT tone at the 5-HT4 receptor in the rat ileum. It is hypothesized that in the presence of fluoxetine, the concentration of endogenous 5-HT at the receptor was increased sufficiently to reduce or abolish the relaxation to 5-HT added exogenously. The inability of fluoxetine to prevent the relaxation to 5-HT in the presence of GR113808 or after the p-CPA treatment supports this hypothesis.
The effect of the selective serotonin reuptake inhibitor fluoxetine was examined on the 5-HT4 receptor-mediated relaxation in the rat isolated ileum.
Fluoxetine unsurmountably antagonized the relaxation to exogenous 5-HT with abolition of the response at 10 ¿M. Fluoxetine (10 ¿M) also caused a gradual loss of the resting tension. These effects of fluoxetine were prevented by a prior addition of the 5-HT4 receptor selective antagonist GR113808 (100 nM), which itself caused a contraction of the tissues when administered alone.
Fluoxetine (10 ¿M) also failed to prevent the relaxation due to exogenous 5-HT and the 5-HT4 receptor agonist 5-methoxytryptamine in tissues taken from the rats treated with para-chlorophenylalanine (300 mg kg¿1) for 3 and 6 days, which reduced the 5-HT level in the mucosa by 88 and 97.5% respectively.
The contraction of the tissues with GR113808 indicates the presence of an endogenous 5-HT tone at the 5-HT4 receptor in the rat ileum. It is hypothesized that in the presence of fluoxetine, the concentration of endogenous 5-HT at the receptor was increased sufficiently to reduce or abolish the relaxation to 5-HT added exogenously. The inability of fluoxetine to prevent the relaxation to 5-HT in the presence of GR113808 or after the p-CPA treatment supports this hypothesis.
Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/2974 |
Date | 13 July 2009 |
Creators | Tuladhar, Bishwa R., Costall, Brenda, Naylor, Robert J. |
Source Sets | Bradford Scholars |
Language | English |
Detected Language | English |
Type | Article, No full-text in the repository |
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