October 1995
Volume 36, Issue 11
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Articles  |   October 1995
Characteristics of [3H]5-hydroxytryptamine binding to iris-ciliary body tissue of the rabbit.
Author Affiliations
  • G Chidlow
    Nuffield Laboratory of Ophthalmology, University of Oxford, United Kingdom.
  • L M De Santis
    Nuffield Laboratory of Ophthalmology, University of Oxford, United Kingdom.
  • N A Sharif
    Nuffield Laboratory of Ophthalmology, University of Oxford, United Kingdom.
  • N N Osborne
    Nuffield Laboratory of Ophthalmology, University of Oxford, United Kingdom.
Investigative Ophthalmology & Visual Science October 1995, Vol.36, 2238-2245. doi:
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    • Get Citation

      G Chidlow, L M De Santis, N A Sharif, N N Osborne; Characteristics of [3H]5-hydroxytryptamine binding to iris-ciliary body tissue of the rabbit.. Invest. Ophthalmol. Vis. Sci. 1995;36(11):2238-2245.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: This study sought to identify, characterize, and localize subtypes of 5-hydroxytryptamine (HT) receptors in rabbit iris-ciliary body. METHODS: Radioligand binding assays were performed with [3H]5-hydroxytryptamine on membranes prepared from rabbit iris-ciliary bodies and on tissue sections subsequently developed by autoradiography. RESULTS: [3H]5-HT appeared to bind to a single population of receptors in membrane preparations of rabbit iris-ciliary body. The apparent affinity of the ligand (KD) was 2.19 nM, and the density of binding sites was 58.3 fmol/mg protein. Binding of [3H] 5-HT exhibited guanosine-5-triphosphate sensitivity. Competitive inhibition experiments were performed to differentiate between 5-HT receptor subtypes. A relative potency order of 5-CT > 5-HT = 8-OH-DPAT > ipsapirone > RU24969 > sumatriptan > ritanserin > ketanserin was demonstrated. The apparent inhibitory constants for the ligands tested fit with the profile expected of binding to 5-HT1A receptors. Inhibition studies with [3H] 5-HT plus 100 nM 8-OH-DPAT (which inhibits binding to 5-HT1A receptors only) representing total binding, indicated that no further displacement occurred when ligands preferentially selective for 5-HT1B, 5-HT1D alpha,1D beta, or 5-HT2C were tested. Total binding of [3H] 5-HT in tissue sections developed by autoradiography was displaced completely by 100 nM 8-OH-DPAT. Melatonin showed little affinity for the [3H] 5-HT binding sites. CONCLUSIONS: A population of 5-HT1A receptors is present in rabbit ciliary processes. There is no evidence to suggest the presence of 5-HT1D alpha, 5-HT1D beta, 5-HT2B, or 5-HT2C receptors in the iris-ciliary body.

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