QUANTITATIVE AUTORADIOGRAPHY OF 5-HT1E BINDING-SITES IN RODENT BRAINS- EFFECT OF LESION OF SEROTONERGIC NEURONS

Binding sites corresponding to 5-HT1E receptors were labelled in mouse , rat, and guinea-pig brains by using [H-3]S-hydroxytryptamine ([H-3]5 -HT) in the presence of 5-carboxamidotryptamine (5-CT) (0.1 mu M), and their distribution within the brain was studied by quantitative autor adiography. The results obtained with mouse brain show that 5-HT1E bin ding sites are particularly present in the cortex, caudate-putamen and claustrum, where they showed the highest density. Lower densities wer e measured in other regions. Saturation experiments showed that the af finity of [H-3]5-HT for 5-HT1E binding sites (nanomolar range) was ver y similar in the different structures. The distribution of 5-HT1E bind ing sites was similar in rat and guinea-pig brains. In rat brain, sele ctive lesioning of serotonergic fibres by intracerebroventricular inje ction of 5,7-dihydroxytryptamine (5,7-DHT), a specific 5-HT neurotoxin , did not affect the density of 5-HT1E binding, indicating that these receptors are mainly localized on non-serotonergic neurones.