Characterization and radioautography of [3H]LSD binding by rat brain slices in vitro: the effect of 5-hydroxytryptamine.

Binding of D-[3H]lysergic acid diethylamide (LSD) to rat coronal brain slices and its blockade by 5-hydroxytryptamine (5-HT) had characteristics similar to those of brain homogenates in respect of KD, kinetics and reversibility of binding. Radioautography was done on slices that had been incubated in 6 nM [3H] LSD and on adjacent slices incubated in the same concentration of tritiated LSD plus 10(-5) M of 5-HT. Choroid plexus showed densest labeling of [3H] LSD. In neuropil, dense labeling occurred within parts of the hippocampal formation except for fields CA2 and CA3 which were sparsely labeled. All layers of the cortex except the posterior cingulate gyrus were labeled by LSD. 5-HT blocked labeling of choroid plexus, hippocampal formation, septum, pons, medulla and parts of cortex but only reduced labeling of most other structures. LSD binding sites may relate to some of its pharmacological effects.