Elsevier

Biochemical Pharmacology

Volume 46, Issue 3, 3 August 1993, Pages 535-538
Biochemical Pharmacology

Short communication
Identification of 5-hydroxytryptamine1D binding sites in sheep caudate nucleus membranes

https://doi.org/10.1016/0006-2952(93)90531-ZGet rights and content

Abstract

Radioligand binding measurements were performed in membranes of sheep caudate nucleus using [3H]5-hydroxytryptamine (5-HT). [3H]5-HT labeled a population of high affinity binding sites with a Kd of 1.9 ± 0.1 nM and a Bmax of 19.8 ± 2.2 mol/mg tissue. Combined 5-HT1D/E binding sites were the predominant 5-HT1 subtype, accounting for 78% of the total population of 5-HT1, binding sites. 5-Carboxamidotryptamine (5-CT) and sumatriptan yielded inhibition curves which best fitted a two-site model with high affinity values of 0.8 and 10.1 nM, and 1000 and 206 nM for their low affinity components. The proportion of the high affinity 5-CT and sumatriptan binding sites was 79 and 72%. The binding affinity profile of 5-HT1D binding sites [5-CT > 5-HT > d-LSD > 5-MeOT > sumatriptan > RU 24, 969 > metergoline > tryptamine = rauwolscine = methylsergide > yohimbine = methiothepin > TFMPP = 8-OH-DPAT > 2-methyl-5-HT > mCPP = quipazine = CP 93, 129 > ketanserin > (-)-propranolol = haloperidol = ipsapirone]compares well to that reported for 5-HT1D receptor sites in human caudate and cortex (correlation coefficient: 0.99 and 0.98). The present results indicate that sheep caudate nucleus is a valid tissue for studying interaction of compounds with 5-HT1D binding sites in the relative absence of 5-HT1E binding sites.

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