Quantitative autoradiography of multiple 5-HT1 receptor subtypes in the brain of control or 5,7-dihydroxytryptamine-treated rats.
The distribution of the 2 main types (A and B) of 5-HT1 binding sites in the rat brain was studied by light-microscopic quantitative autoradiography. The 5-HT1A sites were identified using 3H-8-hydroxy-2-(N-dipropylamino)tetralin (3H-8-OH-DPAT) or 3H-5-HT as the ligand. In the latter case, it was shown that 3H-5-HT binding to 5-HT1A sites corresponded to that displaceable by 0.1 microM 8-OH-DPAT or 1 microM spiperone. The "non-5-HT1A" sites labeled by 3H-5-HT in the presence of 0.1 microM 8-OH-DPAT corresponded mainly to 5-HT1B sites. 5-HT1A binding was notably high in limbic regions (dentate gyrus, CA1 and CA3 hippocampal regions, lateral septum, frontal cortex), whereas 5-HT1B binding was particularly concentrated in extrapyramidal areas (caudate nucleus, globus pallidus, substantia nigra). Except in the latter regions, where only one class of 5-HT1 sites was found, both 5-HT1A and 5-HT1B sites existed in all areas examined. The selective degeneration of serotoninergic neurons produced by an intracerebral injection of 5,7-dihydroxytryptamine was associated only with a significant loss of 5-HT1A binding to the dorsal raphe nucleus (-60%) and of 5-HT1B binding to the substantia nigra (-37%). These results are discussed in relation to the possible identity of 5-HT1A and/or 5-HT1B sites with the presynaptic 5-HT autoreceptors controlling nerve impulse flow and neurotransmitter release in serotoninergic neurons.
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000187:drug effects; D001923:Brain Chemistry; D002421:Caudate Nucleus / Q000032:analysis; D002831:Choroid Plexus / Q000032:analysis; D004102:Dihydroxytryptamines / Q000494:pharmacology*; D005917:Globus Pallidus / Q000032:analysis; D008032:Limbic System / Q000032:analysis; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000032:analysis* / Q000378:metabolism; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism; D013378:Substantia Nigra / Q000032:analysis; D013764:Tetrahydronaphthalenes / Q000378:metabolism; D014018:Tissue Distribution
D004102:Dihydroxytryptamines; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D012110:Reserpine