Supersensitivity of nigral serotonin receptors and rat rotational behaviour.

Direct injections of 5-hydroxytryptamine (5-HT) into the corpus striatum (CS) and substantia nigra (SN) after unilateral 5,7-dihydroxytryptamine (5,7-DHT) of the dorsal raphe nucleus (DRN), resulted in a significant dose related contralateral turning behaviour in SN-injected but not in CS-injected animals. Receptor binding studies in these animals revealed a 3 fold increase in [3H]5-HT binding sites (Bmax) and a similar increase in affinity constant (KD) in the SN from the lesioned side when compared with the unlesioned side. There was no change in binding characteristics in the CS of DRN-lesioned animals. The data presented would confirm our previous findings that nigral 5-HT receptors become supersensitive after denervation of the DRN-SN pathway.