Elsevier

Neuroscience

Volume 17, Issue 1, January 1986, Pages 263-273
Neuroscience

Autoradiographic localization and pharmacology of unique [3H]tryptamine binding sites in rat brain

https://doi.org/10.1016/0306-4522(86)90241-1Get rights and content

Abstract

The distribution and pharmacological specificity of [3H]tryptamine binding to coronal and horizontal sections of the rat brain were investigated with computer-assisted autoradiography. [3H]Tryptamine bound to brain regions with up to 58% specificity, as determined with 10 μM tryptamine as a displacer. The capacity (Bmax) of saturable [3H]tryptamine binding sites was greatest in the nucleus accumbens and claustrum (660–760 fmol mg protein−1), with intermediate binding site concentrations in hippocampus, septum, olfactory tubercle, frontal cortex, cingulate cortex and caudate-putamen. The phenylalkylamine, p-methoxyphenylpropylamine and the β-carboline, harmaline, as well as 5-methyltryptamine, displaced [3H]tryptamine from each of these brain regions with a potency that approximated the 5–9 nM affinity (Kd) of [3H]tryptamine binding to each site. Only micromolar concentrations of serotonin displaced [3H]tryptamine, which did not bind to S1, S2, D1, D2 or alph- or beta-adrenergic sites. The unique pharmacology and the regional overlap of [3H]tryptamine binding sites with dopaminergic nerve terminals in the nucleus accumbens and caudate-putamen suggest that tryptamine-containing neurons in the mammalian brain may modulate behavioral functions such as locomotion.

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